概述
1.概述
此page用以记录leetcode刷题之路，实现语言是c++， 先从简单题开始，后续跟进中等与困难题。
一些注意点：
- 只做算法题。
- 代码尽量使用的是我自己编写的，且经过不断更迭尽量保证时间、空间超过百分之五十以上。
- 实在有不懂的，挑选了评论与题解里面的最优解。
- c++技术不精，还请指正。
- 不定期更新，Github也同步更新，账号：Guotianyu-2020。
2.头文件与cpp文件
1.头文件：
#pragma once
struct ListNode {
int val;
ListNode *next;
ListNode() : val(0), next(nullptr) {}
ListNode(int x) : val(x), next(nullptr) {}
ListNode(int x, ListNode *next) : val(x), next(next) {}
};
struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
TreeNode() : val(0), left(nullptr), right(nullptr) {}
TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
2.cpp
#include<iostream>
#include<cstring>
#include<vector>
#include<cmath>
#include<map>
#include<string>
#include<unordered_set>
#include<unordered_map>
#include<stack>
#include<queue>
#include<cstdlib>
#include<algorithm>
#include<limits.h>
#include<ctype.h>
#include<numeric>
#include<bitset>
#include<random>
#include<time.h>
#include"leetcode_easy_head.h"
using namespace std;
class Leetcode1 // Two Sum
{
public:
class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
int i = 0, j = 0;
vector<int> v;
for (i=0; i<nums.size()-1; i++)
{
for (j = i+1; j<nums.size(); j++)
{
if (nums[i]+nums[j]==target)
{
v.push_back(i);
v.push_back(j);
}
else
{
continue;
}
}
}
return v;
}
void fun1()
{
Solution S;
vector<int> v;
vector<int> o;
v.push_back(3);
v.push_back(2);
v.push_back(4);
int t = 6;
o = S.twoSum(v, t);
for(vector<int>::iterator it = o.begin(); it != o.end(); it++)
{
cout << *it << endl;
}
}
};
};
class Leetcode2 // Reverse Integer
{
public:
class Solution {
public:
int reverse(int x) {
long n = 0;
while(x)
{
n = n * 10 + x % 10;
x /= 10;
}
return n < (-(pow(2, 31))) || n > (pow(2, 31) - 1) ? 0 : n;
}
Solution()
{
int m;
int out;
cout << "leetcode2: input a number to reverse: ";
cin >> m;
out = Solution::reverse(m);
cout << "output: " << out << endl;
}
};
};
class Leetcode3 // Palindrome Number
{
public:
class Solution {
public:
bool isPalindrome(int x) {
if (x<0){return false;}
else
{
long n = 0;
int flag = x;
while (x)
{
n = n * 10 + x % 10;
x /= 10;
}
return n == flag ? true:false;
}
}
Solution()
{
int m;
cout << "input a number to judge: ";
cin >> m;
bool j = isPalindrome(m);
cout << "output(1 == true; 0 == false): " << j << endl;
}
};
};
class Leetcode4 // Roman to Integer
{
public:
class Solution {
public:
int romanToInt(string s) {
int num = 0;
if (s == "IV") {return 4;}
else if(s == "IX"){return 9;}
else if(s == "XL"){return 40;}
else if(s == "XC"){return 90;}
else if(s == "CD"){return 400;}
else if(s == "CM"){return 900;}
else
{
for (int i = 0; i <= s.size(); i++)
{
switch(s[i])
{
case 'I':
if(s[i+1]=='V'){num += 4; i++;}
else if(s[i+1]=='X'){num += 9; i++;}
else{num += 1;}
break;
case 'V':
num += 5;
break;
case 'X':
if(s[i+1]=='L'){num += 40; i++;}
else if(s[i+1]=='C'){num += 90; i++;}
else{num += 10;}
break;
case 'L':
num += 50;
break;
case 'C':
if(s[i+1]=='D'){num += 400; i++;}
else if(s[i+1]=='M'){num += 900; i++;}
else{num += 100;}
break;
case 'D':
num += 500;
break;
case 'M':
num += 1000;
break;
}
}
}
return num;
}
Solution()
{
string ss;
cout << "input roma number: ";
cin >> ss;
int output = romanToInt(ss);
cout << "transfored number: " << output << endl;
}
};
};
class Leetcode5 // Longest Common Prefix
{
public:
class Solution {
public:
string longestCommonPrefix(vector<string>& strs)
{
if (strs.size() == 1){return strs[0];}
string cp = "";
int i = 0, j = 0;
while (j < 200)
{
int count = 0;
char flag = strs[0][j];
for (i = 1; i < strs.size(); i++)
{
if (strs[i][j] && strs[i][j] == flag){ count++ ;}
else
{
return cp;
}
}
if (count + 1 == strs.size())
{
cp += strs[0][j];
}
j++;
}
return cp;
}
Solution()
{
vector<string> v;
v.push_back("a");
v.push_back("flow");
v.push_back("flowadwk");
string output = longestCommonPrefix(v);
cout << "common prefix: " << output << endl;
}
};
};
class Leetcode6 // Judge the legitimacy of the brackets
{
public:
class Solution
{
public:
bool isValid(string s) {
if (s.length() % 2 == 1 || s[0] == ']' || s[0] == '}' ||s[0] == ')' ) {return false;}
else
{
stack<char> sta;
for (int i = 0; i < s.length(); i++)
{
if (s[i] == '[' || s[i] == '{' || s[i] == '(')
{
sta.push(s[i]);
}
else
{
if (sta.size() == 0) {return false;}
else
{
if ((s[i] == ']' && sta.top() == '[') || (s[i] == '}' && sta.top() == '{') || (s[i] == ')' && sta.top() == '(')){sta.pop();}
else {return false;}
}
}
}
return sta.size() == 0 ? true: false;
}
}
Solution()
{
string comma;
cout << "input {}[](): ";
cin >> comma;
bool judge = isValid(comma);
cout << "result: " << judge;
}
};
};
class Leetcode7 // Combine sorted linked list(recursion)
{
public:
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2)
{
if (!l1) {return l2;}
if (!l2) {return l1;}
if (l1->val > l2->val) { return mergeTwoLists(l2, l1); }
l1->next = mergeTwoLists(l1->next, l2);
return l1;
}
Solution()
{
ListNode *l1 = new ListNode(1);
ListNode *l2 = new ListNode(2);
l1->next = l2;
ListNode *l3 = new ListNode(4);
l2->next = l3;
ListNode *l4 = new ListNode(1);
ListNode *l5 = new ListNode(3);
l4->next = l5;
ListNode *l6 = new ListNode(4);
l5->next = l6;
ListNode* lst = mergeTwoLists(l1, l4);
cout << lst->val << endl;
cout << lst->next->val << endl;
cout << lst->next->next->val << endl;
cout << lst->next->next->next->val << endl;
cout << lst->next->next->next->next->val << endl;
cout << lst->next->next->next->next->next->val << endl;
}
};
};
class Leetcode8 // Remove duplicate elements of the sorted array
{
public:
class Solution {
public:
int removeDuplicates(vector<int>& nums)
{
if (nums.size() < 2) return nums.size();
int j = 0;
for (int i = 1; i < nums.size(); i++)
if (nums[j] != nums[i]) nums[++j] = nums[i];
return ++j;
}
Solution()
{
vector<int> nums;
nums.push_back(1);
nums.push_back(1);
nums.push_back(2);
nums.push_back(2);
nums.push_back(2);
nums.push_back(3);
nums.push_back(4);
nums.push_back(5);
nums.push_back(6);
nums.push_back(8);
nums.push_back(8);
nums.push_back(8);
nums.push_back(9);
int j = removeDuplicates(nums);
for (int m = 0; m <j; m++)
{
cout << nums[m] << endl;
}
}
};
};
class Leetcode9 // Remove element
{
public:
class Solution {
public:
int removeElement(vector<int>& nums, int val)
{
/* 垃圾牄1�71ￄ1�771ￄ1�71ￄ1�777
int length = nums.size();
for (int i = 0; i < nums.size()-1; i++)
{
if (nums[i] == val)
{
for (int j = i; j < nums.size()-1; j++)
{
nums[j] = nums[j+1];
}
length--;
if (nums[i] == val)
{
i--;
}
}
}
return length;
*/
// 正向判断的好方法
int k = 0;
for (int i = 0; i < nums.size(); i++)
{
if (nums[i] != val)
{
nums[k++] = nums[i];
}
}
return k;
}
Solution()
{
vector<int> nums;
nums.push_back(3);
nums.push_back(2);
nums.push_back(2);
nums.push_back(3);
nums.push_back(2);
nums.push_back(3);
nums.push_back(4);
nums.push_back(5);
nums.push_back(6);
nums.push_back(8);
nums.push_back(8);
nums.push_back(8);
nums.push_back(9);
int j = removeElement(nums, 3);
cout << j<< endl;
for (int i = 0; i < j; i++) {
cout << nums[i]<< endl;
}
}
};
};
class Leetcode10 // Find substr's position
{
public:
class Solution
{
public:
int strStr(string haystack, string needle) {
if(!needle.size()) return 0;
for(int i = 0; i + needle.size() <= haystack.size(); i ++)
if(haystack.substr(i, needle.size()) == needle) return i; // substr函数做了丢�个切片复制的功能
return -1;
}
Solution()
{
string source = "apple";
string target = "ppl";
int pos = strStr(source, target);
cout << pos << endl;
}
};
};
class Leetcode11 // Find element's position
{
public:
class Solution {
public:
int searchInsert(vector<int>& nums, int target)
{
int i = -1;
for(vector<int>::iterator it = nums.begin(); it != nums.end(); it++)
{
i++;
if (target < *it) {return 0;}
if (*it==target)
{
return i;
}
if (it+1 != nums.end())
{
if (target > (*it) && target < (*(it + 1)))
{
return i+1;
}
}
}
return i + 1;
}
Solution()
{
vector<int>nums = {1, 2, 3, 4, 5};
int pos = searchInsert(nums, 2);
cout << pos << endl;
}
};
};
class Leetcode12 // Look for the sum of the largest subsequences
{
public:
class Solution {
public:
int maxSubArray(vector<int>& nums)
{
int max = INT_MIN;
if (nums.size() == 1){return nums[0];}
for (vector<int>::iterator it = (nums.begin()+1); it != nums.end(); it++)
{
if (*(it-1) < 0){continue;}
else
{
*it += (*(it-1));
}
}
return *max_element(nums.begin(), nums.end());
}
Solution()
{
vector<int> nums = {-1, 2, 3, -4, 5, 7, -3, 4, 6};
int max_num = maxSubArray(nums);
cout << max_num << endl;
}
};
};
class Leetcode13 // Figure out the length of the last word
{
public:
class Solution
{
public:
int lengthOfLastWord(string s)
{
int count = 0, j = 0;
for (j = s.length() - 1; s[j] == ' '; j--);
s = s.substr(0, j);
for (int i = s.length(); i != 0; i--)
{
if (s[i] != ' ' && s[i - 1] != ' ')
{
count++;
}
else if(s[i] != ' ' && s[i-1] == ' '){break;}
}
return count+1;
}
Solution()
{
string ss = "world ";
int len = lengthOfLastWord(ss);
cout << len << endl;
}
};
};
class Leetcode14 // Plus 1
{
public:
class Solution {
public:
vector<int> plusOne(vector<int>& digits) {
int count = 0;
vector<int>::iterator it = digits.end();
vector<int>::iterator iter = it;
if (*(it-1) != 9)
{
*(it-1) += 1;
return digits;
}
for (vector<int>::iterator i = digits.begin(); i != digits.end(); i++)
{
if (*i == 9){ count++;}
}
if (count == digits.size())
{
digits[0] = 1;
for (int i=1; i < digits.size(); i++)
{
digits[i] = 0;
}
digits.push_back(0);
}
else
{
for (iter = digits.end(); *(iter - 1) == 9; iter--);
*(iter-1) += 1;
for (; iter != digits.end(); iter++)
{*iter = 0;}
}
return digits;
}
Solution()
{
vector<int>nums = {1, 9, 9};
nums = plusOne(nums);
for (vector<int>::iterator it = nums.begin(); it !=nums.end(); it++)
{
cout << *it << " ";
}
}
};
};
class Leetcode15 // Binary addition
{
public:
class Solution {
public:
string addBinary(string a, string b)
{
string res="";
int la=a.length(),lb=b.length(),lm=max(la,lb);
//加前导零对齐
for(int i=la;i<lm;i++) a="0"+a;
for(int i=lb;i<lm;i++) b="0"+b;
//进位
int carry=0;
//模拟全加器，分别计算结果和进位�ￄ1�71ￄ1�771ￄ1�71ￄ1�777
for(int i=lm-1;i>=0;i--)
{
/*两位是a,b,上一位进位是c0,这一位进位是c,结果是s
**s=a^b^c0
**c=a&b|(c0&(a^b))
*/
char temp=(a[i]-'0')^(b[i]-'0')^(carry)+'0';
carry=((a[i]-'0')&(b[i]-'0'))|(carry&((a[i]-'0')^(b[i]-'0')));
res=temp+res;
}
//如果算完还有进位，需要补丄1�71ￄ1�771ￄ1�71ￄ1�7771
if(carry==1)
res="1"+res;
return res;
}
Solution()
{
string a = "10111";
string b = "100111001";
string out = addBinary(a, b);
cout << out <<endl;
}
};
};
class Leetcode16 // Square root (Newton iterative method)
{ //https://www.zhihu.com/question/20690553/answer/543620219
public:
class Solution {
public:
int mySqrt(int x)
{
if (x <= 1) return x;
long r = x; // 当x达到INT_MAX时会发生数��溢出，故将原来的int r改为long r
while (r > x / r)
{
r = (r + x / r) / 2;
}
return int(r);
}
Solution()
{
int test = 105;
int rst = mySqrt(test);
cout << rst << endl;
}
};
};
class Leetcode17 // Jump the steps
{
public:
class Solution {
public:
/* 递归方法可以运行但是不够快捷，超出了力扣的时间要汄1�71ￄ1�771ￄ1�71ￄ1�777
int climbStairs(int n)
{
if (n == 1) return 1;
if (n == 2) return 2;
else
{
return climbStairs(n - 1) + climbStairs(n - 2);
}
}
*/
int climbStairs(int n)
{
if (n <= 1) return n;
int dp[3];
dp[1] = 1;
dp[2] = 2;
for (int i = 3; i <= n; i++)
{
int sum = dp[1] + dp[2];
dp[1] = dp[2];
dp[2] = sum;
}
return dp[2];
}
Solution()
{
int num =10;
int ways = climbStairs(num);
cout << ways << endl;
}
};
};
class Leetcode18 // Remove duplicate elements of the sorted list
{
public:
class Solution {
public:
ListNode* deleteDuplicates(ListNode* head)
{
if (!head) {return head;}
ListNode *p = head;
while (p->next)
{
if (p->next->next)
{
if (p->val == p->next->val)
{
p->next = p->next->next;
}
else {p = p->next;}
}
else if (!p->next->next)
{
if (p->val == p->next->val)
{
p->next = nullptr;
}
else break;
}
}
return head;
}
Solution()
{
ListNode l1(2);
ListNode l2(1);
ListNode l3(1);
ListNode l4(3);
ListNode l5(3);
l3.next = &l2;
l2.next = &l1;
l1.next = &l4;
l4.next = &l5;
ListNode* lst = deleteDuplicates(&l3);
cout << lst->val << endl;
cout << lst->next->val << endl;
cout << lst->next->next->val << endl;
}
};
};
class Leetcode19 // Combine arrays
{
public:
class Solution {
public:
void merge(vector<int>& nums1, int m, vector<int>& nums2, int n)
{
if (m == 0) nums1 = nums2;
if (n == 0) nums1 = nums1;
int k = 0;
for (int i = m; i < (m + n); i++)
{
nums1[i] = 513;
}
for (int i = 0; i < m + n; i++)
{
if (nums1[i] > nums2[k])
{
for (int j = m + n - 1; j > i; j--)
{
nums1[j] = nums1[j - 1];
}
nums1[i] = nums2[k++];
if (k == n) { break; }
}
else
{
for (i = i; nums1[i] <= nums2[k]; i++);
i--;
}
}
}
Solution()
{
vector<int>nums1 = {1, 2, 3, 0, 0, 0};
vector<int>nums2 = {2, 4, 6};
merge(nums1, 3, nums2, 3);
for (vector<int>::iterator it = nums1.begin(); it != nums1.end(); it++)
{
cout << *it << endl;
}
}
};
};
class Leetcode20 // Inorder traverse
{
public:
class Solution {
public:
/*垃圾递归
void inorderTraversal(TreeNode* root, vector<int>& nums)
{
if (root->left)
{
inorderTraversal(root->left, nums);
}
nums.push_back(root->val);
if (root->right)
{
inorderTraversal(root->right, nums);
}
}
*/
// 直接遍历
vector<int> inorderTraversal(TreeNode* root)
{
vector<int> res;
stack<TreeNode*> st;
auto p = root; // 自动匹配类型
while (p || !st.empty())
{
while (p)
{
st.push(p);
p = p->left;
}
auto node = st.top();
st.pop();
res.emplace_back(node->val); // 功能和push_back丢�样但是更高效
p = node->right;
}
return res;
}
Solution()
{
TreeNode t0(0);
TreeNode t1(1);
TreeNode t2(2);
TreeNode t3(3);
TreeNode t4(4);
TreeNode t5(5);
TreeNode t6(6);
TreeNode t7(7);
t0.left = &t1;
t0.right = &t2;
t1.left = &t3;
t1.right = &t4;
t2.left = &t5;
t2.right = &t6;
t4.left = &t7;
vector<int> order;
// inorderTraversal(&t0, order); // 递归方式调用
order = inorderTraversal(&t0);
for (vector<int>::iterator it = order.begin(); it != order.end(); it++)
{
cout << *it << endl;
}
}
};
};
class Leetcode21 // Same tree
{
public:
class Solution
{
public:
bool isSameTree(TreeNode* p, TreeNode* q)
{
if (!p && !q) {return true;}
if (!p || !q) {return false;}
if (p->val != q->val) {return false;}
return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
}
Solution()
{
TreeNode* t0 = nullptr;
TreeNode* t1 = nullptr;
cout << isSameTree(t0, t1) << endl;
}
};
};
class Leetcode22 // Symmetric tree
{
public:
class Solution
{
public:
bool isSymmetric(TreeNode* root)
{
if(!root) {return true;}
if (root->left && root->right)
{
bool out = judge(root->left, root->right);
return out;
}
else if (!root->left && !root->right) return true;
else {return false;}
}
bool judge(TreeNode* p, TreeNode* q)
{
if(!p&&!q) return true;
if(!p||!q) return false;
if(p->val==q->val) return judge(p->left,q->right) && judge(p->right,q->left);
return false;
}
Solution()
{
TreeNode* t0 = nullptr;
cout << isSymmetric(t0) << endl;
}
};
};
class Leetcode23 // Max depth of a binary tree
{
public:
class Solution
{
public:
int maxDepth(TreeNode* root)
{
if (!root) {return 0;}
int m = 0, n = 0;
m = maxDepth(root->left);
n = maxDepth(root->right);
return m > n ? m + 1 : n + 1;
}
Solution()
{
TreeNode* t0 = nullptr;
cout << maxDepth(t0) << endl;
}
};
};
class Leetcode24 // Convert Sorted Array to Binary Search Tree
{
public:
class Solution
{
public:
TreeNode* sortedArrayToBST(vector<int>& nums)
{
return build(nums, 0, nums.size()-1);
}
TreeNode* build(vector<int>& nums, int begin, int end)
{
if (begin > end) {return nullptr; }
int middle = begin + (end - begin) / 2;
TreeNode* root = new TreeNode(nums[middle]);
root->left = build(nums, begin, middle - 1);
root->right = build(nums, middle + 1, end);
return root;
}
Solution()
{
vector<int>nums = {-15, -9, -3, -1, 2, 5, 9, 13};
TreeNode* root = sortedArrayToBST(nums);
}
};
};
class Leetcode25 // Balanced Binary Tree
{
public:
class Solution
{
public:
bool isBalanced(TreeNode* root)
{
return inorderTraversal(root);
}
bool inorderTraversal(TreeNode* root)
{
if (root && root->left && root->right)
{
int dl = maxDepth(root->left);
int dr = maxDepth(root->right);
if (abs(dl - dr) > 1) return false;
return inorderTraversal(root->left) && inorderTraversal(root->right);
}
if(root && root->left && !root->right)
{
int dl = maxDepth(root->left);
if (dl > 1) return false;
return true;
}
if(root && !root->left && root->right)
{
int dr = maxDepth(root->right);
if (dr > 1) return false;
return true;
}
if(root && !root->left && !root->right) return true;
else return true;
}
int maxDepth(TreeNode* root)
{
if (!root) {return 0;}
int m = 0, n = 0;
m = maxDepth(root->left);
n = maxDepth(root->right);
return m > n ? m + 1 : n + 1;
}
Solution()
{
cout << "Too lazy to generate an example." << endl;
}
};
};
class Leetcode26 // Minimum Depth of Binary Tree
{
public:
class Solution
{
public:
int minDepth(TreeNode* root)
{
if (!root) return 0;
if (!root->left && root->right) {return minDepth(root->right);}
if (root->left && !root->right) {return minDepth(root->left);}
if (!root->left && !root->right) {return 1;}
else {return min(minDepth(root->left), minDepth(root->right));}
}
Solution()
{
cout << "Too lazy to generate an example." << endl;
}
};
};
class Leetcode27 // Path Sum
{
public:
class Solution
{
public:
bool hasPathSum(TreeNode* root, int targetSum)
{
if (!root) return false;
if (root && !root->left && !root->right && root->val == targetSum) return true;
if (targetSum == root->val && (root->left || root->right)) return hasPathSum(root->left, 0) || hasPathSum(root->right, 0);
return hasPathSum(root->left, targetSum - root->val) || hasPathSum(root->right, targetSum - root->val);
}
Solution()
{
cout << "Too lazy to generate an example." << endl;
}
};
};
class Leetcode28 // Pascal's Triangle
{
public:
class Solution
{
public:
vector<vector<int>> generate(int numRows)
{
vector<vector<int>> nums;
for (int i = 0; i < numRows; i++)
{
vector<int>array(i+1, 1); // Generate 1 with an amount of i.
nums.emplace_back(array);
for (int j = 1; j < i; j++)
{
nums[i][j] = nums[i-1][j-1] + nums[i-1][j];
}
}
return nums;
}
Solution()
{
vector<vector<int>> piscal = generate(4);
}
};
};
class Leetcode29 // Best Time to Buy and Sell Stock
{
public:
class Solution
{
public:
int maxProfit(vector<int>& prices)
{
int max_money = 0;
for (int i = 0; i < prices.size() - 1; i++)
{
int least = min(prices[i], prices[i+1]);
int flag = prices[i+1] - least;
if (flag >= max_money) max_money = flag;
prices[i+1] = (prices[i]==least? prices[i]: prices[i+1]);
}
return max_money;
}
Solution()
{
vector<int> stock = {3, 4, 2, 1, 5, 7, 3, 9, 4};
cout << maxProfit(stock) <<endl;
}
};
};
class Leetcode30 // Valid Palindrome
{
public:
class Solution
{
public:
bool isPalindrome(string s)
{
string ss;
for (int i = 0; i < s.size(); i++)
{
if (isalnum(s[i])) ss += tolower(s[i]);
}
for (int i = 0; i < (ss.size() / 2); i++)
{
if (ss[i] != ss[ss.size()-1-i]) return false;
}
return true;
}
Solution()
{
cout << isPalindrome("woaininiaow") << endl;
}
};
};
class Leetcode31 // Single Number
{
public:
class Solution
{
public:
int singleNumber(vector<int>& nums)
{
int len = nums.size();
int result=0;
for(int i=0;i<len;i++) { result ^=nums[i];}
return result;
}
Solution()
{
vector<int> num = {1, 2, 3, 4, 5, 3, 4, 1, 2};
cout << singleNumber(num) << endl;
}
};
};
class Leetcode32 // Linked List Cycle
{
public:
class Solution
{
public:
/* Trash algorithm
bool hasCycle(ListNode *head)
{
if (!head) return false;
vector<ListNode*> ox;
while (head)
{
ox.emplace_back(head);
head = head->next;
for (int i = 0; i < ox.size(); i++)
{
if (head == ox[i]) return true;
}
}
return false;
}
*/
// fast & slow pointer
bool hasCycle(ListNode *head)
{
if(!head)return false;
ListNode* fast=head->next;
ListNode* slow=head;
while(fast != slow)
{
if(!fast||!fast->next) return false;
fast=fast->next->next;
slow=slow->next;
}
return true;
}
Solution()
{
cout << "To lazy to give an example." << endl;
}
};
};
class Leetcode33 // Pre-order traverse
{
public:
class Solution
{
public:
/* trash recursion
vector<int> preorderTraversal(TreeNode* root)
{
vector<int> nums;
traverse(root, nums);
return nums;
}
void traverse(TreeNode* root, vector<int>& nums)
{
if (root)
{
nums.emplace_back(root->val);
traverse(root->left, nums);
traverse(root->right, nums);
}
}
*/
vector<int> preorderTraversal(TreeNode* root)
{
vector<int> nums;
stack<TreeNode*> rec;
rec.emplace(root);
while(!rec.empty())
{
TreeNode* node = rec.top();
rec.pop();
if (!node) continue;
nums.emplace_back(node->val);
rec.emplace(node->right);
rec.emplace(node->left);
}
return nums;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode34 // Post-order traverse
{
class Solution
{
public:
vector<int> postorderTraversal(TreeNode *root)
{
vector<int> res;
if (root == nullptr) {
return res;
}
stack<TreeNode *> stk;
TreeNode *prev = nullptr;
while (root != nullptr || !stk.empty()) {
while (root != nullptr) {
stk.emplace(root);
root = root->left;
}
root = stk.top();
stk.pop();
if (root->right == nullptr || root->right == prev) {
res.emplace_back(root->val);
prev = root;
root = nullptr;
} else {
stk.emplace(root);
root = root->right;
}
}
return res;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode35 // Minimam stack
{
public:
class Solution
{
public:
class MinStack
{
public:
vector<int> sta;
public:
void push(int val)
{
sta.emplace_back(val);
}
void pop()
{
sta.pop_back();
}
int top()
{
return sta[sta.size()-1];
}
int getMin()
{
if(sta.size()==1) return sta[0];
int min = INT_MAX;
for (vector<int>::iterator it = sta.begin(); it != sta.end(); it++)
{
min = (*it <= min ? *it : min);
}
return min;
}
};
Solution()
{
MinStack mst;
mst.push(1);
mst.push(2);
mst.push(4);
mst.push(-3);
mst.push(5);
mst.push(6);
cout << mst.getMin() << endl;
}
};
};
class Leetcode36 // Intersection of Two Linked Lists
{
public:
// Method1->time: O(n * n); space: O(n)
class Solution
{
public:
ListNode *getIntersectionNodeEasy(ListNode *headA, ListNode *headB)
{
vector<ListNode*> nodes;
ListNode* p1 = headA, * p2 = headB;
while(p1 || p2)
{
if (p1 == p2) return p1;
for (vector<ListNode*>::iterator it = nodes.begin(); it != nodes.end(); it++)
{
if (*it == p1) return p1;
if (*it == p2) return p2;
}
if (p1)
{
nodes.emplace_back(p1);
p1 = p1->next;
}
if (p2)
{
nodes.emplace_back(p2);
p2 = p2->next;
}
}
return nullptr;
}
//Method2->time: O(n); space: O(1)
ListNode *getIntersectionNode(ListNode *headA, ListNode *headB)
{
if (headA == nullptr || headB == nullptr) {return nullptr;}
ListNode *pA = headA, *pB = headB;
while (pA != pB)
{
pA = pA == nullptr ? headB : pA->next;
pB = pB == nullptr ? headA : pB->next;
}
return pA;
}
Solution()
{
ListNode l1 = ListNode(1);
ListNode l2 = ListNode(3);
ListNode l3 = ListNode(5);
ListNode l4 = ListNode(7);
ListNode l5 = ListNode(9);
ListNode l6 = ListNode(30);
ListNode l7 = ListNode(31);
ListNode l8 = ListNode(32);
l1.next = &l2;
l2.next = &l3;
l3.next = &l4;
l4.next = &l5;
l5.next = &l6;
l6.next = &l7;
l7.next = &l8;
ListNode* lst = getIntersectionNodeEasy(&l1, &l6);
string ss = (lst == nullptr? "nullptr": to_string(lst->val));
cout << ss << endl;
}
};
};
class Leetcode37 // Two sum II
{
public:
class Solution
{
public:
vector<int> twoSum(vector<int>& numbers, int target)
{
int l = 0, r = numbers.size() - 1;
vector<int> rec;
while (l < r)
{
if (numbers[l] + numbers[r] == target)
{
rec.emplace_back(l+1);
rec.emplace_back(r+1);
return rec;
}
else if (numbers[l] + numbers[r] < target) l++;
else r--;
}
return rec;
}
Solution()
{
vector<int>nums = {1, 2, 3, 4, 5, 6};
vector<int>output = twoSum(nums, 11);
cout << nums[0] << " " << nums[1] << endl;
}
};
};
class Leetcode38 // Excel Sheet Column Title
{
public:
class Solution
{
public:
string convertToTitle(int columnNumber)
{
vector<char> table;
string ss;
for (int i = 0; i < 27; i++)
{
table.emplace_back((i + 64));
}
table[0] = 'Z';
while (columnNumber)
{
int quotient = columnNumber / 26;
int remainder = columnNumber % 26;
if (columnNumber % 26 == 0)
{
quotient--;
}
ss += table[remainder];
if (!quotient) break;
columnNumber = quotient;
}
reverse(ss.begin(), ss.end()); // Pay attention to reversing a string.
return ss;
}
Solution()
{
string ss = convertToTitle(701);
cout << ss << endl;
}
};
};
class Leetcode39 // Majority Element
{
public:
class Solution
{
public:
/* My method: count numbers. But uses sort().
int majorityElement(vector<int>& nums)
{
sort(nums.begin(), nums.end());
int turn = 0;
for (int i = 0; i < nums.size(); i++)
{
int flag = nums[i];
if( (i != 0) && (flag != nums[i-1])) turn = 1;
else turn++;
if (turn > (nums.size() / 2)) return nums[i];
}
return 0;
}
*/
/* Simplest way with sort: if a snake hides in a tube which is not longer than twice of the snake,
/* you can cut the snake by cutting the middle of the tube
int majorityElement(vector<int>& nums)
{
sort(nums.begin(), nums.end());
return nums[nums.size() / 2];
}
*/
// Good method: moore vote
int majorityElement(vector<int>& nums)
{
int count=1;
int temp=nums[0];
int n=nums.size();
for(int i=1;i<n;i++)
{
if(nums[i]==temp) count++;
else count--;
if(count==0)
{
temp=nums[i+1];
i++;
count=1;
}
}
return temp;
}
Solution()
{
vector<int>nums = {1, 1, 2 ,2, 2};
cout << majorityElement(nums) << endl;
}
};
};
class Leetcode40 // Excel Sheet Column Number
{
public:
class Solution
{
public:
int titleToNumber(string columnTitle)
{
int num = 0;
long power = 1;
for (int i = columnTitle.size() - 1; i >= 0; i--)
{
num += (int(columnTitle[i]) - 64) * power;
power *= 26;
}
return num;
}
Solution()
{
cout << titleToNumber("AB") <<endl;
}
};
};
class Leetcode41 // reverseBits
{
public:
class Solution
{
public:
uint32_t reverseBits(uint32_t n)
{
uint32_t ans=0;
int i=32;
while(i--)
{
ans<<=1;
ans+=n&1;
n>>=1;
}
return ans;
}
Solution()
{
uint32_t num = 43261596;
cout << bitset<32>(reverseBits(num)) << endl;
}
};
};
class Leetcode42 // Happy number
{
public:
class Solution
{
public:
bool isHappy(int n)
{
int m = 0;
int sum = 0;
int length = to_string(n).size();
while (sum != 1)
{
while (n)
{
int flag = pow(10, (length--) - 1);
m = n / flag;
n -= flag * m;
sum += pow(m, 2);
}
if (sum == 4) return false;
if (sum == 1) return true;
n = sum;
sum = 0;
length = to_string(n).size();
}
return true;
}
Solution()
{
cout << isHappy(19) << endl;
}
};
};
class Leetcode43 // Remove Linked List Elements
{
public:
class Solution
{
public:
ListNode* removeElements(ListNode* head, int val)
{
struct ListNode* dummyHead = new ListNode(0, head);
// 这里是直接创建了丢�个初始化了的ListNode的指针，与下面先生成结点ListNode l1(7)，再设置内容的方法不同��加不加struct好像没有区别〄1�71ￄ1�77
struct ListNode* temp = dummyHead;
while (temp->next != NULL) {
if (temp->next->val == val) {
temp->next = temp->next->next;
} else {
temp = temp->next;
}
}
return dummyHead->next;
}
Solution()
{
ListNode l1(7);
ListNode l2(7);
ListNode l3(7);
ListNode l4(7);
l1.next = &l2;
l2.next = &l3;
l3.next = &l4;
ListNode* lst = removeElements(&l1, 7);
while (lst)
{
cout << lst->val << endl;
lst = lst->next;
}
}
};
};
class Leetcode44 // Isomorphic Strings
{
public:
class Solution
{
public:
bool isIsomorphic(string s, string t) // my method
{
map<char, char> dict;
for (int i = 0; i < s.size(); i++)
{
if (!dict.count(s[i]))
{
for(map<char,char>::iterator it = dict.begin(); it != dict.end(); it++)
{
if( it->second == t[i]) return false;
}
dict.insert(make_pair(s[i], t[i]));
}
else
{
if ((*(dict.find(s[i]))).second == t[i]) continue;
else return false;
}
}
return true;
}
bool isIsomorphicOther(string s, string t) // other method
{
for(int i = 0; i < s.size(); ++i)
{
if(s.find(s[i]) != t.find(t[i])) return false;
}
return true;
}
Solution()
{
cout << isIsomorphic("badc", "baba") << endl;
}
};
};
class Leetcode45 // Reverse Linked List
{
public:
class Solution
{
public:
ListNode* reverseListIteration(ListNode* head) // iteration, a little bit slow
{
if (!head) return nullptr;
ListNode* root = new ListNode(head->val);
while (head->next)
{
ListNode* newNode = new ListNode(head->next->val, root);
root = newNode;
head = head->next;
}
return root;
delete(root);
}
ListNode* reverseList(ListNode* head)
{
if (!head || !head->next) {
return head;
}
ListNode* newHead = reverseList(head->next);
head->next->next = head;
head->next = nullptr;
return newHead;
}
Solution()
{
ListNode* head = new ListNode(5);
head = reverseList(head);
cout << head->val << endl;
delete head;
}
};
};
class Leetcode46 // Contains Duplicate I
{
public:
class Solution
{
public:
/* simple way
bool containsDuplicate(vector<int>& nums)
{
return set<int>(nums.begin(), nums.end()).size() != nums.size();
}
*/
bool containsDuplicate(vector<int>& nums)
{
sort(nums.begin(), nums.end());
for (int i = 0; i < nums.size() - 1; i++)
{
if (nums[i]== nums[i+1]) return true;
}
return false;
}
Solution()
{
vector<int>number = {1, 2, 3, 4, 5, 6};
cout << containsDuplicate(number) << endl;
}
};
};
class Leetcode47 // Contains Duplicate II
{
public:
class Solution
{
public:
bool containsNearbyDuplicateBrutal(vector<int>& nums, int k) // Runtime overflow
{
if (nums.size() == 0 || nums.size() == 1) return false;
for (int i = 0; i < nums.size() - 1; i++)
{
for (int j = i + 1; j <= i + k; j++)
{
if ( j < nums.size() && nums[i] == nums[j] ) return true;
}
}
return false;
}
bool containsNearbyDuplicate(vector<int>& nums, int k)
{
unordered_set<int> existed;
int n = nums.size();
int curr = 0;
for (int i = 0; i < n; ++i)
{
curr = nums[i];
if (existed.find(curr) == existed.end())
{
existed.insert(curr);
if (existed.size() > k) existed.erase(nums[i-k]);
}
else return true;
}
return false;
}
Solution()
{
vector<int>nums = {12, 23, 1, 2, 3};
cout << containsNearbyDuplicate(nums, 5) << endl;
}
};
};
class Leetcode48 // Implement Stack using Queues
{
public:
class MyStack
{
public:
queue<int> q1;
queue<int> q2;
public:
void push(int x)
{
q1.push(x);
}
int pop()
{
int flag = 0;
int num = q1.size() - 1;
while (flag != num - 1)
{
q2.push(q1.front());
q1.pop();
flag++;
}
int rec = q1.front();
q1.pop();
q1 = q2;
q2 = {};
return rec;
}
int top()
{
return q1.back();
}
bool empty()
{
if (q1.size() == 0) return true;
return false;
}
};
class Solution
{
public:
Solution()
{
MyStack mst;
mst.push(1);
mst.push(2);
int l1 = mst.top();
int l2 = mst.pop();
int l4 = mst.empty();
cout << l1 << endl;
cout << l2 << endl;
cout << l4 << endl;
}
};
};
class Leetcode49 // Invert a binary tree
{
public:
class Solution
{
public:
TreeNode* invertTree(TreeNode* root)
{
if (root == nullptr) return nullptr;
TreeNode* left = invertTree(root->left);
TreeNode* right = invertTree(root->right);
root->left = right;
root->right = left;
return root;
}
Solution()
{
cout << "Too lazy to generate a binary tree." << endl;
}
};
};
class Leetcode50 // Summary Ranges
{
public:
class Solution
{
public:
vector<string> summaryRangesMyMethod(vector<int>& nums) // My method: works on vscode but can't work on leetcode(time over flow)
{
if (nums.empty()) return {};
if (nums.size() == 1) return {to_string(nums[0])};
int flag = 0;
vector<int>rec;
vector<string>output;
for (int i = 0; i < nums.size(); i++)
{
int flag = nums[i];
rec.emplace_back(nums[i]);
// while ( (nums[i++]) == (nums[i]++) );
while (nums[i + 1] && nums[i + 1] == nums[i] + 1)
{
i++;
}
if (nums[i] == flag) output.emplace_back(to_string(flag));
else
{
if (i != nums.size() - 1)
{
rec.emplace_back(nums[i]);
output.emplace_back(to_string(rec[rec.size() - 2]) + "->" + to_string(rec[rec.size() - 1]));
rec.emplace_back(nums[i + 1]);
}
else
{
rec.emplace_back(nums[i]);
output.emplace_back(to_string(rec[rec.size() - 2]) + "->" + to_string(rec[rec.size() - 1]));
}
}
}
return output;
}
vector<string> summaryRanges(vector<int>& nums) // official answer
{
vector<string> ret;
int i = 0;
int n = nums.size();
while (i < n)
{
int low = i;
i++;
while (i < n && nums[i] == nums[i - 1] + 1)
{
i++;
}
int high = i - 1;
string temp = to_string(nums[low]);
if (low < high)
{
temp.append("->");
temp.append(to_string(nums[high]));
}
ret.push_back(move(temp));
}
return ret;
}
Solution()
{
vector<int> nums = {0, 1};
vector<string> out = summaryRanges(nums);
for (int i = 0; i < out.size(); i++)
{
cout << out[i] << endl;
}
}
};
};
class Leetcode51 // Power of two
{
public:
class Solution
{
public:
bool isPowerOfTwoRecursion(int n) // recursion
{
if (n == 0) return false;
if (n == 1) return true;
if (n % 2 == 1) return false;
else return isPowerOfTwoRecursion(n / 2);
}
bool isPowerOfTwo(int n) // solve it without loops/recursion
{
if (n < 1) return false;
return (n & n-1) == 0; // 8(1000) & 7(0111) == 0(0000)
}
Solution()
{
cout << isPowerOfTwo(3738) << endl;
}
};
};
class Leetcode52 // Implement Queue using Stacks
{
public:
class MyQueue
{
private:
stack<int> a;
stack<int> b;
public:
void push(int x) {a.push(x);}
int pop()
{
int num = 0;
if (b.empty())
{
while(!a.empty())
{
b.push(a.top());
a.pop();
}
}
if (!b.empty())
{
num = b.top();
b.pop();
}
return num;
}
int peek()
{
int num = 0;
if (b.empty())
{
while(!a.empty())
{
b.push(a.top());
a.pop();
}
}
if (!b.empty())
num = b.top();
return num;
}
bool empty()
{
if (a.empty() && b.empty())
return true;
return false;
}
};
class Solution
{
Solution()
{
cout << "No example here." << endl;
}
};
};
class Leetcode53 // Palindrome Linked List
{
public:
class Solution
{
public:
bool isPalindromeMethodSector(ListNode* head) // not the best answer. Time complex = Space complex = O(n)
{
vector<int> rec;
ListNode* p = head;
while (p)
{
rec.emplace_back(p->val);
p = p->next;
}
for (int i = 0; i <= rec.size() / 2; i++)
{
if (rec[i] != rec[rec.size() - 1 - i]) return false;
}
return true;
}
bool isPalindrome(ListNode* head) // official answer
{
if (head == nullptr || head->next == nullptr) return true;
ListNode* slow = head; // 慢指针，找到链表中间分位置，作为分割
ListNode* fast = head;
ListNode* pre = head; // 记录慢指针的前一个节点，用来分割链表
while (fast && fast->next)
{
pre = slow;
slow = slow->next;
fast = fast->next->next;
}
pre->next = nullptr; // 分割链表
ListNode* cur1 = head; // 前半部分
ListNode* cur2 = reverseList(slow); // 反转后半部分，��链表长度如果是奇数，cur2比cur1多一个节炄1�71ￄ1�77
// 弢�始两个链表的比较
while (cur1)
{
if (cur1->val != cur2->val) return false;
cur1 = cur1->next;
cur2 = cur2->next;
}
return true;
}
// 反转链表
ListNode* reverseList(ListNode* head)
{
ListNode* temp; // 保存cur的下丢�个节炄1�71ￄ1�77
ListNode* cur = head;
ListNode* pre = nullptr;
while(cur)
{
temp = cur->next; // 保存丢�丄1�71ￄ1�77 cur的下丢�个节点，因为接下来要改变cur->next
cur->next = pre; // 翻转操作
// 更新pre 咄1�71ￄ1�77 cur指针
pre = cur;
cur = temp;
}
return pre;
}
Solution()
{
ListNode l1(1);
ListNode l2(2);
ListNode l3(3);
l1.next = &l2;
l2.next = &l3;
cout << isPalindrome(&l1) << endl;
}
};
};
class Leetcode54 // Lowest Common Ancestor of a Binary Search Tree
{
public:
class Solution
{
public:
TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q)
{
if (root == p || root == q) return root;
if (root->val > p->val && root->val < q->val) return root;
else if (root->val > p->val && root->val > q->val)
{
return lowestCommonAncestor(root->left, p, q);
}
else if (root->val < p->val && root->val < q->val)
{
return lowestCommonAncestor(root->right, p, q);
}
return root;
}
Solution()
{
cout << "To lazy to generate a tree." << endl;
}
};
};
class Leetcode55 // Delete Node in a Linked List (not a good problem...)
{
public:
class Solution
{
public:
void deleteNode(ListNode* node)
{
node->val = node->next->val;
node->next = node->next->next;
}
Solution()
{
cout << "This is not a good question..." << endl;
}
};
};
class Leetcode56 // Valid Anagram
{
public:
class Solution
{
bool isAnagram(string s, string t) // method1
{
sort(s.begin(),s.end());
sort(t.begin(),t.end());
return s == t? true : false;
}
bool isAnagramWithMap(string s, string t) // method2
{
if (s.size() != t.size()) return false;
unordered_map<char, int> dict;
for (int i = 0; i < s.size(); i++)
{
++dict[s[i]];
--dict[t[i]];
}
for(unordered_map<char,int>::iterator it = dict.begin();it != dict.end(); it++)
{
if(it->second != 0) return false;
}
return true;
}
Solution()
{
cout << isAnagram("asdsa", "dsasa") << endl;
}
};
};
class Leetcode57 // Binary Tree Paths (hard for me...)
{
public:
class Solution
{
public:
vector<string> binaryTreePaths(TreeNode* root) // recursion
{
vector<string> output;
goThrough(root, output, "");
return output;
}
void goThrough(TreeNode* root, vector<string>& output, string path)
{
if (root != nullptr) path += to_string(root->val);
if (!root->left && !root->right) output.emplace_back(path);
if (root->left) goThrough(root->left, output, path + "->");
if (root->right) goThrough(root->right, output, path + "->");
}
Solution()
{
cout << "Too lazy to generate a binary tree." << endl;
}
/* iteration. Official answer.
class Solution {
public:
vector<string> binaryTreePaths(TreeNode* root) {
vector<string> paths;
if (root == nullptr) {
return paths;
}
queue<TreeNode*> node_queue;
queue<string> path_queue;
node_queue.push(root);
path_queue.push(to_string(root->val));
while (!node_queue.empty()) {
TreeNode* node = node_queue.front();
string path = path_queue.front();
node_queue.pop();
path_queue.pop();
if (node->left == nullptr && node->right == nullptr) {
paths.push_back(path);
} else {
if (node->left != nullptr) {
node_queue.push(node->left);
path_queue.push(path + "->" + to_string(node->left->val));
}
if (node->right != nullptr) {
node_queue.push(node->right);
path_queue.push(path + "->" + to_string(node->right->val));
}
}
}
return paths;
}
};
*/
};
};
class Leetcode58 // Add Digits
{
public:
class Solution
{
public:
int addDigits(int num) // recursion
{
if (num < 10) return num;
return addDigits(((num / 10) + (num % 10)));
}
int addDigitsMath(int num) // math
{
if (num == 0) return 0;
return num % 9 == 0 ? 9 : num % 9;
}
Solution()
{
cout << addDigits(1565312) << endl;
cout << addDigitsMath(1565312) << endl;
}
};
};
class Leetcode59 // Ugly Number
{
public:
class Solution
{
public:
bool isUgly(int n)
{
if (n == 0) return false;
if (n == 1 || n == 2 || n == 3 || n == 5) return true;
else
{
if (n % 2 == 0) return isUgly(n / 2);
if (n % 3 == 0) return isUgly(n / 3);
if (n % 5 == 0) return isUgly(n / 5);
return false;
}
}
Solution()
{
cout << isUgly(113114) << endl;
}
};
};
class Leetcode60 // Missing Number
{
public:
class Solution
{
public:
int missingNumber(vector<int>& nums) // My method 1
{
sort(nums.begin(), nums.end());
for (int i = 0; i < nums.size(); i++)
{
if (nums[i] != i) return i;
}
return nums.size();
}
int missingNumber2(vector<int>& nums) // My method 2
{
int res = nums.size();
for (int i = 0; i < nums.size(); ++i){
res ^= nums[i];
res ^= i;
}
return res;
}
// good method
int missingNumber3(vector<int>& nums)
{
int res = nums.size();
for (int i = 0; i < nums.size(); ++i)
{
res ^= nums[i];
res ^= i;
}
return res;
}
Solution()
{
vector<int>nums = {1 , 2, 3, 0};
cout << missingNumber(nums) << endl;
}
};
};
class Leetcode61 // Move Zeros
{
public:
class Solution
{
public:
void moveZeroes(vector<int>& nums)
{
int n = nums.size(), left = 0, right = 0;
while (right < n)
{
if (nums[right])
{
swap(nums[left], nums[right]);
left++;
}
right++;
}
}
Solution()
{
vector<int>nums = {0, 1, 0};
moveZeroes(nums);
for (int i = 0; i < nums.size(); i++)
{
cout << nums[i] << endl;
}
}
};
};
class Leetcode62 // Nim Game
{
public:
class Solution
{
public:
bool canWinNim(int n)
{
return n % 4 == 0 ? false : true;
}
Solution()
{
cout << canWinNim(152) << endl;
}
};
};
class Leetcode64 // Power Of Three
{
public:
class Solution
{
public:
bool isPowerOfThree(int n)
{
return n > 0 && 1162261467 % n == 0;
}
Solution()
{
cout << isPowerOfThree(1314) << endl;
}
};
};
class Leetcode65 // Count 1
{
public:
class Solution
{
public:
vector<int> countBits(int n)
{
vector<int> res(n + 1);
for (int i = 1; i <= n; i++)
{
res[i] = res[i & (i - 1)] + 1; // i & (i - 1)总会让i少一丄1�71（最右边的一位），返回去的参照位置不各1�7
}
return res;
}
Solution()
{
vector<int>nums = countBits(5);
for (int i = 0; i < nums.size(); i++)
{
cout << nums[i] << endl;
}
}
};
};
class Leetcode66 // Power Of 4
{
public:
class Solution
{
public:
bool isPowerOfFour(int n)
{
if (n == 0) return false;
while (n % 4 == 0)
{
n >>= 2;
}
return n == 1 ? true : false;
}
Solution()
{
cout << isPowerOfFour(438) << endl;
}
};
};
class Leetcode67 // Reverse a string
{
public:
class Solution
{
public:
void reverseString(vector<char>& s)
{
for (int i = 0, j = s.size() - 1; i < s.size() / 2; i++, j--)
{
swap(s[i], s[j]);
}
}
Solution()
{
vector<char> s = {'a', 's', 'k'};
reverseString(s);
cout << s[0] << s[1] << s[2] << endl;
}
};
};
class Leetcode68 // Reverse Vowels of a String
{
public:
class Solution
{
public:
string reverseVowels(string s)
{
int left = 0, right = s.size() - 1;
vector<char> vowels = {'a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'};
while (left < right)
{
vector<char>::iterator it_left = find(vowels.begin(), vowels.end(), s[left]);
vector<char>::iterator it_right = find(vowels.begin(), vowels.end(), s[right]);
if (it_left != vowels.end() && it_right != vowels.end()) {swap(s[left], s[right]); right--; left++;}
else if (it_left == vowels.end() && it_right != vowels.end()) left++;
else if (it_left != vowels.end() && it_right == vowels.end()) right--;
else {right--; left++;}
}
return s;
}
Solution()
{
string ss = reverseVowels("hello");
cout << ss << endl;
}
};
};
class Leetcode69 // Intersection of Two Arrays(I)
{
public:
class Solution
{
public:
vector<int> intersection(vector<int>& nums1, vector<int>& nums2)
{
unordered_set<int> output;
unordered_set<int> nums(nums1.begin(), nums1.end()); // 把nums1去重
for (int i : nums2)
{
if (nums.find(i) != nums.end()) output.insert(i); // 插入时把nums2去重
}
return vector<int>(output.begin(), output.end());
}
Solution()
{
vector<int>a {1, 2, 3, 3};
vector<int>b {2, 3, 3, 4};
vector<int> num = intersection(a, b);
for (int i : num)
{
cout << i << endl;
}
}
};
};
class Leetcode70 // Intersection of Two Arrays(II)
{
public:
class Solution
{
public:
vector<int> intersect(vector<int>& nums1, vector<int>& nums2)
{
vector<int> rst;
for (int i : nums1)
{
vector<int>::iterator it = find(nums2.begin(), nums2.end(), i);
if (it != nums2.end())
{
rst.emplace_back(i);
nums2.erase(it);
}
}
return rst;
}
Solution()
{
vector<int>n1 = {1, 2, 3, 6, 5, 2, 3, 2, 3, 2, 21, 2, 3};
vector<int>n2 = {1, 3, 4, 5, 3, 2, 1};
vector<int>n3 = intersect(n1, n2);
for (int i : n3)
{
cout << i << endl;
}
}
};
};
class Leetcode71 // Valid Perfect Square
{
public:
class Solution
{
public:
bool isPerfectSquare(int num)
{
if (num == 1) return true;
long sum = 0;
for (int i = 1; i <= num - 1; i += 2)
{
sum += i;
if (sum == num) return true;
if (sum > num) return false;
}
return num == sum ? true : false;
}
Solution()
{
cout << isPerfectSquare(314159) << endl;
}
};
};
class Leetcode72 // Ransom Note
{
public:
class Solution
{
public:
bool canConstruct(string ransomNote, string magazine)
{
unordered_map<char, int> table;
for (int i = 0; i < ransomNote.size(); i++)
{
if (table.find(ransomNote[i]) == table.end())
{
table.emplace(ransomNote[i], 1);
}
else
{
table.find(ransomNote[i])->second++;
}
}
for (int i = 0; i < magazine.size(); i++)
{
if (table.find(magazine[i]) != table.end())
{
((table.find(magazine[i]))->second)--;
}
}
for (unordered_map<char, int>::iterator it = table.begin(); it != table.end(); it++)
{
if (it->second > 0) return false;
}
return true;
}
/* 箢�化版
bool canConstruct(string ransomNote, string magazine)
{
unordered_map<char,int> mag;
for(char c : magazine)
{
mag[c]++;
}
for(char c : ransomNote)
{
mag[c]--;
if(mag[c] < 0) return false;
}
return true;
}
*/
Solution()
{
cout << canConstruct("bg", "bgg") << endl;
}
};
};
class Leetcode73 // First Unique Character in a String
{
public:
class Solution
{
public:
int firstUniqChar(string s)
{
unordered_map<char, int> rst;
for (char i : s)
{
rst[i]++;
}
for (int i = 0; i < s.size(); i++)
{
if (rst[s[i]] == 1) return i;
}
return -1;
}
Solution()
{
cout << firstUniqChar("leetcode") << endl;
}
};
};
class Leetcode74 // Find the Difference
{
public:
class Solution
{
public:
char findTheDifference(string s, string t)
{
int sum = 0;
for (auto i : t)
sum += i;
for (auto i : s)
sum -= i;
return sum;
}
Solution()
{
cout << findTheDifference("abbcd", "cbbgad") << endl;
}
};
};
class Leetcode75 // Is Subsequence
{
public:
class Solution
{
public:
bool isSubsequence(string s, string t)
{
int flag = 0;
for (int i = 0; i < t.size(); i++)
{
if (t[i] == s[flag])
{
flag++;
}
}
return flag == s.size() ? true : false;
}
Solution()
{
cout << isSubsequence("asd","asaooodpjkofenod") << endl;
}
};
};
class Leetcode76 // Binary Watch
{
public:
class Solution {
public:
vector<string> readBinaryWatch(int turnedOn)
{
vector<string> rst;
for (int i = 0; i <= 11; i++)
{
for (int j = 0; j <= 59; j++)
{
if (__builtin_popcount(i) + __builtin_popcount(j) == turnedOn)
{
rst.emplace_back(to_string(i) + ":" + + (j < 10 ? "0" : "") + to_string(j));
}
}
}
return rst;
}
Solution()
{
vector<string> out = readBinaryWatch(2);
for(string i: out)
{
cout << i << endl;
}
}
};
};
class Leetcode77 // Sum of Left Leaves
{
public:
class Solution
{
public:
int sumOfLeftLeaves(TreeNode* root)
{
if (!root) return 0;
int res = 0;
if (root->left && !root->left->left && !root->left->right) res += root->left->val;
return sumOfLeftLeaves(root->left) + sumOfLeftLeaves(root->right) + res;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode78 // Convert a Number to Hexadecimal
{
public:
class Solution
{
public:
string toHex(long num) // 为什么传入long，因为案侄1�7-2147483648转化为正数不能传进来
{
string tab = "0123456789abcdef";
string rem = "";
int left = 0;
if (num == 0) return "0";
if (num >= 0)
{
while (num)
{
rem += tab[num % 16];
num = num / 16;
}
int right = rem.size() - 1;
while (left < right)
{
swap(rem[left], rem[right]);
left++;
right--;
}
return rem;
}
else
{
int flag = 0;
string out1 = toHex(-num);
out1 = string(8 - out1.size(), '0') + out1;
string out2 = "";
for (int j = out1.size() - 1; out1[j] == '0'; j--, flag++);
for (int i = 0; i < (7 - flag) ; i++)
{
out2 += tab[15 - tab.find(out1[i])];
}
out2 += tab[16 - tab.find(out1[7 - flag])];
for (int i = 0; i != flag; i++) out2 += '0';
return out2;
}
}
/* 把传入的参数改为无符号类型可以避免分类讨讄1�7
string toHex(unsigned int num)
{
constexpr auto str = "0123456789abcdef"; // 定义变量时可以用 constexpr 修饰，从而使该变量获得在编译阶段即可计算出结果的能力〄1�7
string ans;
while (num)
{
ans += str[num & 0xf];
num >>= 4;
}
reverse(ans.begin(), ans.end());
return ans.empty() ? "0" : ans;
}
*/
Solution()
{
cout << toHex(-100000) << endl;
}
};
};
class Leetcode79 // Longest Palindrome
{
public:
class Solution
{
public:
int longestPalindrome(string s)
{
unordered_map<char, int> table;
int sum = 0, flag = 0;
for (char i : s) table[i]++;
for (unordered_map<char, int>::iterator it = table.begin(); it != table.end(); it++)
{
if (it->second % 2 == 0) sum += it->second;
else
{
sum += (it->second - 1);
flag++;
}
}
if (flag != 0) sum++;
return sum;
}
Solution()
{
cout << longestPalindrome("dwauihwaiuesiufisnuieiufiuainidawi") << endl;
}
};
};
class Leetcode80 // FizzBuzz
{
public:
class Solution
{
public:
vector<string> fizzBuzz(int n)
{
vector<string> rst;
for (int i = 1; i < n + 1; i++)
{
rst.emplace_back(judge(i));
}
return rst;
}
string judge(int n)
{
if (n % 15 == 0) return "FizzBuzz";
if (n % 5 == 0) return "Buzz";
if (n % 3 == 0) return "Fizz";
return to_string(n);
}
Solution()
{
vector<string>ss = fizzBuzz(1355);
for (string i : ss) cout << i << " ";
}
};
};
class Leetcode81 // Third Maximum Number
{
public:
class Solution
{
public:
int thirdMax(vector<int>& nums) // 此方法用到的sort函数时间复杂度为O(nlogn),还可以改迄1�7
{
if (nums.size() == 1) return nums[0];
if (nums.size() == 2)
{
return nums[0] > nums[1] ? nums[0] : nums[1];
}
else
{
sort(nums.begin(), nums.end());
nums.erase(unique(nums.begin(), nums.end()), nums.end()); // unique函数去重
if (nums.size() < 3) return thirdMax(nums);
return nums[nums.size() - 3];
}
return 0;
}
/*直接丢�次遍历，时间复杂度O(n)
int thirdMax(vector<int> &nums)
{
long a = LONG_MIN, b = LONG_MIN, c = LONG_MIN;
for (long num : nums)
{
if (num > a)
{
c = b;
b = a;
a = num;
} else if (a > num && num > b)
{
c = b;
b = num;
} else if (b > num && num > c)
{
c = num;
}
}
return c == LONG_MIN ? a : c;
}
*/
Solution()
{
vector<int>nums = {1, 2, 3, 6, 6, 4, 3, 8, 4, 3};
cout << thirdMax(nums) << endl;
}
};
};
class Leetcode82 // Add Strings
{
public:
class Solution
{
public:
string addStrings(string num1, string num2)
{
string str;
int cur = 0, i = num1.size()-1, j = num2.size()-1;
while (i >= 0 || j >= 0 || cur != 0)
{
if (i >= 0) cur += num1[i--] - '0';
if (j >= 0) cur += num2[j--] - '0';
str += to_string (cur % 10);
cur /= 10;
}
reverse(str.begin(), str.end());
return str;
}
Solution()
{
cout << addStrings("1298918908634869879434684496013", "498676232283682678767831838678775353141413178675453143512") << endl;
}
};
};
class Leetcode83 // Number of Segments in a String
{
public:
class Solution
{
public:
int countSegments(string s)
{
s += ' ';
int cnt = 0;
for (int i = 0; i < s.size() - 1; i++) {
if (s[i] != ' ' && s[i + 1] == ' ') {
cnt++;
}
}
return cnt;
}
Solution()
{
cout << countSegments("asd fgh jhgfr, ., hu") << endl;
}
};
};
class Leetcode84 // Arranging Coins
{
public:
class Solution {
public:
int arrangeCoins(int n)
{
int i = 1;
for (; n >= i; i++) n -= i;
return --i;
}
int arrangeCoinsBinary(int n) // 二分泄1�7
{
return (-1+sqrt(1+(long long int)8*n))/2;
}
Solution()
{
cout << arrangeCoins(1352668311) << endl;
}
};
};
class Leetcode85 // Find All Numbers Disappeared in an Array
{
public:
class Solution {
public:
vector<int> findDisappearedNumbers(vector<int>& nums)
{
for (int i = 0; i < nums.size(); ++i)
nums[abs(nums[i])-1] = -abs(nums[abs(nums[i])-1]); // 考虑到了反转两次的情冄1�7
vector<int> res;
for (int i = 0; i < nums.size(); ++i)
{
if (nums[i] > 0)
res.push_back(i+1);
}
return res;
}
Solution()
{
vector<int>num = {1, 3, 5, 2, 1, 3, 5, 2, 6, 4, 3};
num = findDisappearedNumbers(num);
for (int i : num)
{
cout << i << " ";
}
}
};
};
class Leetcode86 // Minimum Moves to Equal Array Elements
{
public:
class Solution {
public:
int minMoves(vector<int>& nums)
{
int sum = 0, min = nums[0];
for (int i : nums) if (i < min) min = i;
for (int i : nums) sum += (i - min);
return sum;
}
Solution()
{
vector<int>nums = {1, 3, 8};
cout << minMoves(nums) << endl;
}
};
};
class Leetcode87 // Assign Cookies
{
public:
class Solution
{
public:
int findContentChildren(vector<int>& g, vector<int>& s)
{
sort(g.begin(), g.end());
sort(s.begin(), s.end());
int i = 0, j = 0;
for (; i < g.size() && j < s.size(); i++, j++)
{
if (g[i] > s[j])
{
while (s[j] < g[i])
{
if (j != s.size() - 1) j++;
else return i;
}
}
}
return i;
}
/*箢�化版
int findContentChildren(vector<int>& g, vector<int>& s)
{
sort(g.begin(),g.end());
sort(s.begin(),s.end());
int index = 0;
for(int i = 0;i < s.size();++i)
{
if(index < g.size() && g[index] <= s[i]) index++;
}
return index;
}
*/
Solution()
{
vector<int>children = {1, 2, 3};
vector<int>biscuit = {1, 1};
cout << findContentChildren(children, biscuit) << endl;
}
};
};
class Leetcode88 // Repeated Substring Pattern (hard for me)
{
public:
class Solution
{
public:
bool repeatedSubstringPattern(string s)
{
return (s + s).find(s, 1) != s.size(); // 用kmp算法代替find函数效率更高
}
Solution()
{
cout << repeatedSubstringPattern("aaabbbcdcdaaabbbcdcd") << endl;
}
};
};
class Leetcode89 // Hamming Distance
{
public:
class Solution {
public:
int hammingDistance(int x, int y)
{
int d = 0;
int z = x ^ y;
while (z != 0) {
z = z & (z - 1);
d++;
}
return d;
}
/*使用内置函数计算二进制数丄1�71的个敄1�7
return __builtin_popcount(x ^ y);
*/
Solution()
{
cout << hammingDistance(25, 52) << endl;
}
};
};
class Leetcode90 // Island Perimeter
{
public:
class Solution {
public:
int islandPerimeter(vector<vector<int>>& grid)
{
int total = 0;
for (int i = 0; i < grid.size(); i++) // 对行进行处理
{
for (int j = 0; j < grid[i].size(); j++) // 对列进行处理
{
if (grid[i][j] == 1)
{
total += 4;
if (i != grid.size() - 1 && grid[i][j] == grid[i + 1][j]) total--;
if (i != 0 && grid[i][j] == grid[i - 1][j]) total--;
if (j != grid[i].size() - 1 && grid[i][j] == grid[i][j + 1]) total--;
if (j != 0 && grid[i][j] == grid[i][j - 1]) total--;
}
}
}
return total;
}
Solution()
{
vector<vector<int>> island = {{0,1,0,0},{1,1,1,0},{0,1,0,0},{1,1,0,0}};
cout << islandPerimeter(island) << endl;
}
};
};
class Leetcode91 // Number Complement
{
public:
class Solution {
public:
int findComplement(int num)
{
int highbit = 0;
for (int i = 1; i <= 30; ++i) // 找到num二进制的朢�高位
{
if (num >= (1 << i))
{
highbit = i;
}
else break;
}
int mask = (highbit == 30 ? 0x7fffffff : (1 << (highbit + 1)) - 1); // 此处分类是为了防止溢出，将num与同位数的全1进行异或即为扢�汄1�7
return num ^ mask;
}
/* 上面方法的精箢�牄1�7
int findComplement(int num)
{
int temp = num, c = 0;
while(temp > 0){
temp >>= 1;
c = (c << 1) + 1; // 直接得到与num同位数的兄1�71敄1�7
}
return num ^ c;
}
*/
Solution()
{
cout << findComplement(12) << endl;
}
};
};
class Leetcode92 // License Key Formatting
{
public:
class Solution {
public:
string licenseKeyFormatting(string s, int k)
{
string ans;
int cnt = 0;
for (int i = s.size() - 1; i >= 0; i--)
{
if (s[i] != '-')
{
ans.push_back(toupper(s[i]));
cnt++;
if (cnt % k == 0)
{
ans.push_back('-');
}
}
}
if (ans.size() > 0 && ans.back() == '-')
{
ans.pop_back();
}
reverse(ans.begin(), ans.end());
return ans;
}
Solution()
{
cout << licenseKeyFormatting("asdkdsa", 3) << endl;
}
};
};
class Leetcode93 // Max Consecutive Ones
{
public:
class Solution
{
public:
int findMaxConsecutiveOnes(vector<int>& nums)
{
int max = 0;
for (int i = 1; i < nums.size(); i++)
{
if (nums[i - 1] && nums[i]) nums[i] += nums[i - 1];
}
for (int i : nums) max = (i >= max ? i : max);
return max;
}
Solution()
{
vector<int>num = {0, 1, 1, 0, 1, 1, 1};
cout << findMaxConsecutiveOnes(num) << endl;
}
};
};
class Leetcode94 // Construct the Rectangle
{
public:
class Solution {
public:
vector<int> constructRectangle(int area)
{
int wide=sqrt(area);
while(area % wide!=0){
wide--;
}
return vector<int>{area/wide,wide};
}
Solution()
{
for (int i : constructRectangle(53))
{
cout << i << " ";
}
}
};
};
class Leetcode95 // Teemo Attacking
{
public:
class Solution
{
public:
int findPoisonedDuration(vector<int>& timeSeries, int duration)
{
int total = 0;
for (int i = 0; i < timeSeries.size() - 1; i++)
{
if (timeSeries[i] + duration > timeSeries[i + 1]) total += timeSeries[i + 1] - timeSeries[i];
else total += duration;
}
total += duration;
return total;
}
Solution()
{
vector<int> a{1, 2, 3, 4};
cout << findPoisonedDuration(a, 3) << endl;
}
};
};
class Leetcode96 // Next Greater Element I
{
public:
class Solution {
public:
vector<int> nextGreaterElement(vector<int>& nums1, vector<int>& nums2)
{
stack<int> s;
map<int, int> m;
vector<int> rst(nums1.size(), -1);
for (int i : nums2)
{
if (s.empty()) s.push(i);
else
{
if (i < s.top()) s.push(i);
else
{
while (!s.empty() && s.top() < i)
{
m[s.top()] = i;
s.pop();
}
s.push(i);
}
}
}
for (int i = 0; i < nums1.size(); i++)
{
map<int, int>::iterator pos = m.find(nums1[i]);
if (pos != m.end()) rst[i] = pos->second;
}
return rst;
}
Solution()
{
vector<int> n1 = {1, 2, 7, 5, 4, 6};
vector<int> n2 = {1, 2, 7, 5, 4, 6};
for (int i: nextGreaterElement(n1, n2))
cout << i <<endl;
}
};
};
class Leetcode97 // Keyboard Row
{
public:
class Solution
{
public:
vector<string> findWords(vector<string>& words)
{
string row1 = "qwertyuiopQWERTYUIOP", row2 = "asdfghjklASDFGHJKL", row3 = "zxcvbnmZXCVBNM";
vector<string> rst;
for (string i : words)
{
int flag = 0;
string cmp;
for (char j : i)
{
if (flag == 0)
{
if (find(row1.begin(), row1.end(), j) != row1.end()) cmp = row1;
if (find(row2.begin(), row2.end(), j) != row2.end()) cmp = row2;
if (find(row3.begin(), row3.end(), j) != row3.end()) cmp = row3;
}
if (find(cmp.begin(), cmp.end(), j) == cmp.end()) break;
flag++;
}
if (flag == i.size()) rst.emplace_back(i);
}
return rst;
}
Solution()
{
vector<string> str = {"asdfghjklASDFGHJKL", "qwertyuiopQWERTYUIOP", "zxcvbnmZXCVBNM"};
for (string i : findWords(str))
{
cout << i << " ";
}
}
};
};
class Leetcode98 // Find Mode in Binary Search Tree
{
public:
class Solution
{
public:
// 我的方法，太慢了
vector<int> InorderTraverseMy(TreeNode* root, vector<int>& nums)
{
if (root->left) InorderTraverseMy(root->left, nums);
nums.emplace_back(root->val);
if (root->right) InorderTraverseMy(root->right, nums);
return nums;
}
vector<int> findModeMy(TreeNode* root)
{
vector<int> nums, out;
multimap<int, int, greater<int>> rst;
nums = InorderTraverseMy(root, nums);
int count = 1;
for (int i = 1; i < nums.size(); i++)
{
if (nums[i] == nums[i - 1]) count++;
else
{
rst.insert(make_pair(count, nums[i - 1]));
count = 1;
}
}
rst.insert(make_pair(count, nums[nums.size() - 1]));
multimap<int, int>::iterator it = rst.begin(), it1 = rst.begin();
it1++;
out.emplace_back(it->second);
for (; it1 != rst.end() ; it1++)
{
if (it1->first == it->first) out.emplace_back(it1->second);
}
return out;
}
// 以上是我的方泄1�7
// 评论区优质方法，不使用额外空间，思想就是在中序遍历的过程中直接比较当前结点与上一个结点的值大小关系并计数
void inOrder(TreeNode* root, TreeNode*& pre, int& curTimes, int& maxTimes, vector<int>& res)
{
if (!root) return;
inOrder(root->left, pre, curTimes, maxTimes, res);
if (pre)
curTimes = (root->val == pre->val) ? curTimes + 1 : 1;
if (curTimes == maxTimes)
res.push_back(root->val);
else if (curTimes > maxTimes)
{
res.clear();
res.push_back(root->val);
maxTimes = curTimes;
}
pre = root;
inOrder(root->right, pre, curTimes, maxTimes, res);
}
vector<int> findMode(TreeNode* root)
{
vector<int> res;
if (!root) return res;
TreeNode* pre = NULL;
int curTimes = 1, maxTimes = 0;
inOrder(root, pre, curTimes, maxTimes, res);
return res;
}
Solution()
{
TreeNode t3(2);
TreeNode t2(1, nullptr, &t3);
//TreeNode t1(1, nullptr, &t2);
for (int i : findMode(&t2))
{
cout << i << endl;
}
}
};
};
class Leetcode99 // Base 7
{
public:
class Solution {
public:
string convertToBase7(int num)
{
int rem = 0;
string ss = "";
if (num == 0) return "0";
if (num < 0) return "-" + convertToBase7(-num);
while (num)
{
rem = num % 7;
num = num / 7;
ss += to_string(rem);
}
reverse(ss.begin(), ss.end());
return ss;
}
Solution()
{
cout << convertToBase7(53) << endl;
}
};
};
class Leetcode100 // Relative Ranks
{
public:
class Solution {
public:
vector<string> findRelativeRanks(vector<int>& score)
{
int max_score = *max_element(score.begin(), score.end()); // 获取分数的最大��1�7
vector<int> index(max_score + 1, -1); // 申请丢�个包含max+1个全昄1�7-1的数组1�7
for(int i = 0; i < score.size(); i++)
{
index[score[i]] = i;
}
vector<string> ret(score.size(),"");
int rank = score.size(); // 排名
int j = 0 ; // index数组的下标��1�7
while(rank > 0){
if(index[j] != -1){
if(rank == 1) { ret[index[j]] = "Gold Medal"; }
else if(rank == 2){ ret[index[j]] = "Silver Medal"; }
else if(rank == 3){ ret[index[j]] = "Bronze Medal"; }
else{ ret[index[j]] = to_string(rank); }
rank --;
}
j++;
}
return ret;
}
Solution()
{
vector<int> score = {5, 4, 3, 2, 1};
for (string i : findRelativeRanks(score))
{
cout << i << endl;
}
}
};
};
class Leetcode101 // Perfect Number
{
public:
class Solution
{
public:
bool checkPerfectNumberMy(int num)
{
int sum = 0;
for (int i = 1; i <= num / 2; i++)
{
if (num % i == 0) sum += i;
}
return sum == num ? true : false;
}
bool checkPerfectNumber(int num)
{
if (num==1) return false;
int sum = 1, i = 2;
for (; i * i < num; ++i)
{
if (num % i == 0) sum+=i, sum+= num/i;
}
return sum == num;
}
Solution()
{
cout << checkPerfectNumber(28) << endl;
}
};
};
class Leetcode102 // Fibnacci
{
public:
class Solution
{
public:
int fib_recursion(int n) // 递归
{
if (n < 2) return n;
return fib_recursion(n - 1) + fib_recursion(n - 2);
}
int fib_dp(int N) // 动��规刄1�7
{
if (N <= 1) return N;
vector<int> dp(N + 1);
dp[0] = 0;
dp[1] = 1;
for (int i = 2; i <= N; i++)
{
dp[i] = dp[i - 1] + dp[i - 2];
}
return dp[N];
}
Solution()
{
cout << fib_dp(12) << endl;
}
};
};
class Leetcode103 // Detect Capital
{
public:
class Solution
{
public:
bool case1(string word)
{
string words;
for (char i : word) words += toupper(i);
if (word == words) return true;
return false;
}
bool case2(string word)
{
string words;
words += toupper(word[0]);
for (int i = 1; i < word.size(); i++) words += tolower(word[i]);
if (word == words) return true;
return false;
}
bool case3(string word)
{
string words;
for (char i : word) words += tolower(i);
if (word == words) return true;
return false;
}
bool detectCapitalUse(string word)
{
return case1(word) || case2(word) || case3(word);
}
Solution()
{
cout << detectCapitalUse("FlaG") << endl;
}
};
};
class Leetcode104 // Longest Uncommon Subsequence I
{
public:
class Solution
{
public:
int findLUSlength(string a, string b)
{
if (a.size() > b.size()) return a.size();
if (a.size() < b.size()) return b.size();
if (a == b) return -1;
return a.size();
}
Solution()
{
cout << findLUSlength("aaa", "bbb") << endl;
}
};
};
class Leetcode105 // Minimum Absolute Difference in BST
{
public:
class Solution
{
public:
int getMinimumDifference(TreeNode* root)
{
vector<int>nums;
inOrderTraverse(root, nums);
int min = nums[nums.size() - 1];
for (int i = 0; i < nums.size() - 1; i++)
{
min = (nums[i + 1] - nums[i] < min ? nums[i + 1] - nums[i] : min);
}
return min;
}
void inOrderTraverse(TreeNode* root, vector<int>& nums)
{
if (!root);
if (root->left) inOrderTraverse(root->left, nums);
nums.emplace_back(root->val);
if (root->right) inOrderTraverse(root->right, nums);
}
Solution()
{
cout << "Too lazy to generate a tree.";
}
};
};
class Leetcode106 // Reverse String II
{
public:
class Solution
{
public:
string reverseStr(string s, int k)
{
for (int i = 0; i < s.size(); i += 2 * k)
{
if (i + k <= s.size())
{
reverse(s.begin() + i, s.begin() + i + k);
} else {
reverse(s.begin() + i, s.end());
}
}
return s;
}
Solution()
{
cout << reverseStr("abcdefg", 4) << endl;
}
};
};
class Leetcode107 // Diameter of Binary Tree
{
public:
class Solution
{
int ans;
int depth(TreeNode* rt)
{
if (rt == NULL) return 0; // 访问到空节点了，返回0
int L = depth(rt->left); // 左儿子为根的子树的深庄1�7
int R = depth(rt->right); // 右儿子为根的子树的深庄1�7
ans = max(ans, L + R + 1); // 计算d_node即L+R+1 并更新ans
return max(L, R) + 1; // 返回该节点为根的子树的深庄1�7
}
public:
int diameterOfBinaryTree(TreeNode* root) {
ans = 1;
depth(root);
return ans - 1;
}
Solution()
{
cout << "Too lazy to generate a tree" << endl;
}
};
};
class Leetcode108 // Student Attendance Record I
{
public:
class Solution
{
public:
bool checkRecord(string s) {
int times = s.size(), abs = 0, cons_l = 0, max_cons_l = 0;
for (int i = 0; i < times; i++)
{
if (s[i] == 'A') abs++;
if (abs >= 2) return false;
if (s[i] == 'L')
{
cons_l = 0;
while (s[i] == 'L')
{
cons_l++;
i++;
}
max_cons_l = (cons_l > max_cons_l ? cons_l : max_cons_l);
i--;
}
if (max_cons_l > 2) return false;
}
return true;
}
/* 评论区一行代码版：find正向查找，rfind逆向查找
return (s.find("LLL")==-1) && (s.find('A')==s.rfind('A'));
or:
return s.find("LLL") == std::string::npos && std::count(s.begin(), s.end(), 'A') < 2;
*/
Solution()
{
cout << checkRecord("LPLLPLL") << endl;
}
};
};
class Leetcode109 // Reverse Words in a String III
{
public:
class Solution
{
public:
string reverseWords(string s)
{
for(int i = 0; i < s.size(); i ++)
{
if(s[i] == ' ') continue;
int j = i;
while(j < s.size() && s[j] != ' ') j ++;
reverse(s.begin() + i, s.begin() + j);
i = j;
}
return s;
}
Solution()
{
cout << reverseWords("I'm a big boy.") << endl;
}
};
};
class Leetcode110 // Maximum Depth of N-ary Tree
{
public:
class Solution
{
public:
int maxDepth(Node* root)
{
if (!root) return 0;
if (root->children.empty()) return 1;
vector<int> nums(root->children.size());
for (int i = 0; i < root->children.size(); i++)
{
nums[i] = maxDepth(root->children[i]);
}
return *max_element(nums.begin(),nums.end()) + 1;
}
/*来自评论区的优化算法
int maxDepth(Node* root)
{
if (root == 0) return 0;
int depth = 0;
for (int i = 0; i < root->children.size(); i++)
{
depth = max (depth, maxDepth(root->children[i])); // 这一步很巧妙，在动态中寻找最大值
}
return depth + 1;
}
*/
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode111 // Array Partition I
{
public:
class Solution
{
public:
int arrayPairSum(vector<int>& nums)
{
int sum = 0;
sort(nums.begin(), nums.end());
for (int i = 0; i < nums.size(); i += 2)
{
sum += nums[i];
}
return sum;
}
Solution()
{
vector<int>nums = {1, 2, 3, 4};
cout << arrayPairSum(nums) << endl;
}
};
};
class Leetcode112 // Binary Tree Tilt
{
public:
class Solution
{
private:
int p = 0;
public:
int findTilt(TreeNode* root)
{
if (!root) return 0;
dfs(root);
return p;
}
int dfs(TreeNode* root)
{
if (root->left && root->right)
{
int left = dfs(root->left);
int right = dfs(root->right);
p += abs(left - right);
return left + right + root->val;
}
if (!root->left && !root->right) return root->val;
else if (root->left)
{
int left = dfs(root->left);
p += abs(left);
return left + root->val;
}
else
{
int right = dfs(root->right);
p += abs(right);
return right + root->val;
}
return 0;
}
/*简化版dfs函数
int dfs(TreeNode* root)
{
if (!root)
{
return 0;
}
int left = dfs(root->left);
int right = dfs(root->right);
p += abs(left - right);
return left + right + root->val;
}
*/
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode113 // Subtree of Another Tree
{
public:
class Solution
{
public:
bool isSameTree(TreeNode* s, TreeNode* t)
{
if (!s && !t) return true;
return s && t && s->val == t->val && isSameTree(s->left, t->left) && isSameTree(s->right, t->right);
}
bool isSubtree(TreeNode* root, TreeNode* subRoot)
{
if (!root && !subRoot) return true;
if (!root) return false;
return isSameTree(root, subRoot) || isSubtree(root->left, subRoot) || isSubtree(root->right, subRoot);
}
Solution()
{
cout << "Too lazy to generate a tree" << endl;
}
};
};
class Leetcode114 // Distribute Candies
{
public:
class Solution
{
public:
int distributeCandies(vector<int>& candyType)
{
sort(candyType.begin(), candyType.end());
int l = candyType.size() / 2;
int num = 1;
for (int i = 1; i < candyType.size(); i++) if (candyType[i] != candyType[i - 1]) num++;
return num > l ? l : num;
}
Solution()
{
vector<int> nums = {1, 2, 3, 4, 5, 6, 9, 8, 7, 6, 5, 4};
cout << distributeCandies(nums) << endl;
}
};
};
class Leetcode115 // N-ary Tree Preorder Traversal
{
public:
class Solution
{
public:
vector<int> nums;
stack<Node*> sta;
vector<int> preorder(Node* root) // recursion
{
if (!root) return nums;
nums.emplace_back(root->val);
for (int i = 0; i < root->children.size(); i++)
{
preorder(root->children[i]);
}
return nums;
}
vector<int> preorderIter(Node* root)
{
if (!root) return nums;
sta.push(root);
while (!sta.empty())
{
auto cur = sta.top();
sta.pop();
nums.push_back(cur->val);
int n = (cur->children.size());
for (int i = n - 1; i >= 0; i--)
{
if (cur->children[i]) sta.push(cur->children[i]);
}
}
return nums;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode116 // N-ary Tree Postorder Traversal
{
public:
class Solution
{
public:
vector<int> nums;
vector<int> postorder(Node* root)
{
if (!root) return nums;
if (root->children.size() != 0)
{
for (int i = 0; i < root->children.size(); i++)
{
postorder(root->children[i]);
}
}
else
{
nums.emplace_back(root->val);
}
return nums;
}
vector<int> postorder2(Node* root)
{
stack<Node*> st;
vector<int> res;
if(!root) return {};
st.push(root);
while(!st.empty())
{
Node* node = st.top();
st.pop();
res.push_back(node->val);
int n = node->children.size();
for(int i = 0; i < n; i ++) if (node->children[i]) st.push(node->children[i]);
}
reverse(res.begin(),res.end());
return res;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode117 // Longest Harmonious Subsequence
{
public:
class Solution
{
public:
int findLHS(vector<int>& nums)
{
sort(nums.begin(), nums.end());
int p1 = 0, p2 = 0;
for (int i = 0; i < nums.size(); i++)
{
while (nums[i] - nums[p1] > 1) p1++;
if (nums[i] - nums[p1] == 1) p2 = max(p2, i - p1 + 1);
}
return p2;
}
Solution()
{
vector<int>nums = {1, 2, 3, 2, 1};
cout << findLHS(nums) << endl;
}
};
};
class Leetcode118 // Range Addition II
{
public:
class Solution {
public:
int maxCount(int m, int n, vector<vector<int>>& ops)
{
int m1 = m, n1 = n;
for(int i = 0; i < ops.size(); i++)
{
m1 = min(m1,ops[i][0]);
n1 = min(n1,ops[i][1]);
}
return m1 * n1;
}
Solution()
{
vector<vector<int>> ops = {{1, 2}, {2, 3}};
cout << maxCount(5, 5, ops) << endl;
}
};
};
class Leetcode119 // Minimum Index Sum of Two Lists
{
public:
class Solution
{
public:
vector<string> findRestaurant(vector<string>& list1, vector<string>& list2)
{
unordered_map<string, int> rec;
int iter = 0, flag = 0;
int min = INT_MAX;
vector<string>rst;
for (string i : list1)
{
rec.emplace(i, iter++);
}
for (int j = 0; j < list2.size(); j++)
{
if (rec.count(list2[j]))
{
if (flag == 0)
{
min = j + rec[list2[j]];
rst.emplace_back(list2[j]);
flag++;
}
else
{
if (min == j + rec[list2[j]]) rst.emplace_back(list2[j]);
if (min > j + rec[list2[j]])
{
min = j + rec[list2[j]];
rst.clear();
rst.emplace_back(list2[j]);
}
}
}
}
return rst;
}
Solution()
{
vector<string> list1 = {"aaa", "bbb", "ccc"};
vector<string> list2 = {"bbb", "ccc", "ddd"};
for (string i : findRestaurant(list1, list2))
{
cout << i << endl;
}
}
};
};
class Leetcode120 // Can Place Flowers
{
public:
class Solution {
public:
bool canPlaceFlowers(vector<int>& flowerbed, int n)
{
if (n == 0) return true;
int plantable = 0;
for (int i = 0; i < flowerbed.size(); i++)
{
if (i == 0 && flowerbed[i] == 0)
{
plantable++;
flowerbed[i] = 1;
}
if (i > 0)
{
if (flowerbed[i] == 0 && flowerbed[i - 1] != 1)
{
plantable++;
flowerbed[i] = 1;
}
if (flowerbed[i] == 1 && flowerbed[i - 1] == 1)
{
plantable--;
}
}
}
return (plantable >= n ? true : false);
}
Solution()
{
vector<int> nums = {1, 0, 0, 0, 1};
cout << canPlaceFlowers(nums, 2) << endl;
}
};
};
class Leetcode121 // Construct String from Binary Tree
{
public:
class Solution
{
public:
string tree2str(TreeNode* root) // 思路不是很清晰
{
if (!root) return "";
string ss = "";
preOrderTraverse(root, ss);
ss = ss.substr(0, ss.length() - 1);
return ss;
}
void preOrderTraverse(TreeNode * root, string& s)
{
if (root)
{
s += to_string(root->val);
if (root->left && root->right) s += "(";
if (!root->left && !root->right) s += ")";
if (!root->left && root->right) s += "()(";
if (!root->right && root->left) s += "(";
}
if (root->left)
{
preOrderTraverse(root->left, s);
if (!root->right) s += ")";
if (root->right) s += "(";
}
if (root->right)
{
preOrderTraverse(root->right, s);
s += ")";
}
}
/* 评论区的方法，更加直接和简洁*/
string tree2strBetter(TreeNode* t)
{
string res = "";
if(t==NULL) return res;
if(t->left==NULL && t->right == NULL)
{
res.append(to_string(t->val));
return res;
}
res.append(to_string(t->val));
res+=("("+tree2str(t->left)+")");
if(t->right!=NULL)
res+=("("+tree2str(t->right)+")");
return res;
}
Solution()
{
cout << "Too lazy to generate a tree.";
}
};
};
class Leetcode122 // Merge Two Binary Trees
{
public:
class Solution
{
public:
TreeNode* mergeTrees(TreeNode* root1, TreeNode* root2)
{
if (!root1 && !root2) return nullptr;
if (!root1) return root2;
if (!root2) return root1;
if (root1 && root2)
{
root1->val += root2->val;
if (root1->left && root2->left) mergeTrees(root1->left, root2->left);
if (root1->right && root2->right) mergeTrees(root1->right, root2->right);
if (!root1->left && root2->left)
{
if (!root2->left->left && !root2->left->right)
{
root1->left = new TreeNode(root2->left->val);
}
else if (root2->left->left && !root2->left->right)
{
root1->left = new TreeNode(root2->left->val, root2->left->left, nullptr);
}
else if (!root2->left->left && root2->left->right)
{
root1->left = new TreeNode(root2->left->val, nullptr, root2->left->right);
}
else
{
root1->left = new TreeNode(root2->left->val, root2->left->left, root2->left->right);
}
}
if (!root1->right && root2->right)
{
if (!root2->right->left && !root2->right->right)
{
root1->right = new TreeNode(root2->right->val);
}
else if (root2->right->left && !root2->right->right)
{
root1->right = new TreeNode(root2->right->val, root2->right->left, nullptr);
}
else if (!root2->right->left && root2->right->right)
{
root1->right = new TreeNode(root2->right->val, nullptr, root2->right->right);
}
else
{
root1->right = new TreeNode(root2->right->val, root2->right->left, root2->right->right);
}
}
}
return root1;
}
/* 官方题解，深度搜索*/
TreeNode* mergeTreesDFS(TreeNode* t1, TreeNode* t2)
{
if (t1 == nullptr) return t2;
if (t2 == nullptr) return t1;
auto merged = new TreeNode(t1->val + t2->val);
merged->left = mergeTrees(t1->left, t2->left);
merged->right = mergeTrees(t1->right, t2->right);
return merged;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode123 // Maximum Product of Three Numbers
{
public:
class Solution
{
public:
int maximumProduct(vector<int>& nums)
{
sort(nums.begin(), nums.end());
return max(nums[nums.size() - 1] * nums[nums.size() - 2] * nums[nums.size() - 3], nums[nums.size() - 1] * nums[0] * nums[1]);
}
Solution()
{
vector<int> nums = {1, 2, 3, 4};
cout << maximumProduct(nums) << endl;
}
};
};
class Leetcode124 // Average of Levels in Binary Tree
{
public:
class Solution
{
public:
vector<double> averageOfLevels(TreeNode* root)
{
queue<TreeNode*> que;
if (root != NULL) que.push(root);
vector<double> result;
while (!que.empty())
{
int size = que.size();
double sum = 0; // 统计每一层的和
for (int i = 0; i < size; i++)
{
TreeNode* node = que.front();
que.pop();
sum += node->val;
if (node->left) que.push(node->left);
if (node->right) que.push(node->right);
}
result.push_back(sum / size); // 将每一层均值放进结果集
}
return result;
}
Solution()
{
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode125 // Maximum Average Subarray I
{
public:
class Solution
{
public:
double findMaxAverage(vector<int>& nums, int k)
{
double sum = 0;
double aver = 0;
for (int i = 0; i < k; i++)
{
sum += nums[i];
}
aver = sum / k;
for (int i = k; i < nums.size(); i++)
{
sum = sum + nums[i] - nums[i - k];
aver = double(sum / k) > aver ? double(sum / k) : aver;
}
return aver;
}
Solution()
{
vector<int> nums = {4,2,1,3,3};
cout << findMaxAverage(nums, 2) << endl;
}
};
};
class Leetcode126 // Set Mismatch
{
public:
class Solution {
public:
vector<int> findErrorNums(vector<int>& nums) {
vector<int> rst(2);
sort(nums.begin(), nums.end());
if (nums[0] == 1) {
for (int i = 0; i < nums.size(); i++) {
if (i != 0 && nums[i] == nums[i - 1]) {
rst[0] = nums[i];
}
else if (i != 0 && nums[i] - nums[i - 1] != 1) {
rst[1] = nums[i - 1] + 1;
}
if (rst[0] && rst[1]) return rst;
}
rst[1] = nums[nums.size() - 1] + 1;
return rst;
} else {
rst[1] = 1;
for (int i = 1; i < nums.size(); i++) {
if (nums[i] == nums[i - 1]) {
rst[0] = nums[i];
return rst;
}
}
}
return rst;
}
Solution() {
vector<int> nums = {1, 2, 3, 3};
nums = findErrorNums(nums);
for (int i: nums) cout << i << " ";
}
};
};
class Leetcode127 { // Two Sum IV - Input is a BST
public:
class Solution {
public:
bool findTarget(TreeNode* root, int k) {
vector<int> nums;
inorderTraverse(root, nums);
int left = 0, right = nums.size() - 1;
while (left < right) {
if ((nums[left] + nums[right]) == k) return true;
if ((nums[left] + nums[right]) < k) left++;
if ((nums[left] + nums[right]) > k) right--;
}
return false;
}
void inorderTraverse(TreeNode* root, vector<int>& nums) {
if (root && root->left) inorderTraverse(root->left, nums);
if (root) nums.emplace_back(root->val);
if (root->right) inorderTraverse(root->right, nums);
}
Solution() {
cout << "Too lazy to generate a tree." << endl;
}
};
};
class Leetcode128 { // Robot Return to Origin
public:
class Solution {
public:
bool judgeCircle(string moves) {
vector<int> judge = {0, 0};
for (int i = 0; i < moves.size(); i++) {
if (moves[i] == 'R') judge[0]++;
if (moves[i] == 'L') judge[0]--;
if (moves[i] == 'U') judge[1]++;
if (moves[i] == 'D') judge[1]--;
}
return (judge[0] == 0 && judge[1] == 0 ? true : false);
}
Solution() {
cout << judgeCircle("LLDDLL") << endl;
}
};
};
int main()
{
//查看题目结果格式：Leetcodex::Solution sx;
Leetcode126::Solution s14;
system("pause");
return 0;
}
最后
以上就是无限柚子为你收集整理的Leetcode简单题（不定期更新）的全部内容，希望文章能够帮你解决Leetcode简单题（不定期更新）所遇到的程序开发问题。
如果觉得靠谱客网站的内容还不错，欢迎将靠谱客网站推荐给程序员好友。
本图文内容来源于网友提供，作为学习参考使用，或来自网络收集整理，版权属于原作者所有。
发表评论 取消回复