Python刷题常用数据结构

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head = ListNode()
head.next = ListNode(val)

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dump = ListNode(0, head)

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sets = set()
sets.add(val1)
sets.remove(val2)
#判断这个数是否在集合中：
s[right + 1] not in sets

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hashtable = dict()
#直接赋值
hashtable[nums[i]] = i
#查字典
hashtable.get(键)
#遍历完排序！
res =[(x,y) for x,y in hashset.items()]
res.sort()

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from collections import defaultdict
res = defaultdict(int/list)

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''.join(a)

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"".join(a[::-1])

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ord(s)
chr(a)

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a = 'deLDE'
a = a.lower()
a = a.upper()

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import string
cor = {v: i for i, v in enumerate(string.ascii_lowercase)}
cor2 = {v: i for i, v in enumerate(string.ascii_uppercase)}

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mat = [[''] * c for _ in range(r)]

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''.join(ch for row in mat for ch in row if ch)

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matrix_B[:] = matrix_A   #√
matrix_B = matrix_A #×

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zip(*matrix)

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import heapq #载入heap库，heap指的是最小堆

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heap = [1,3,4,2,6,8,9]
heapq.heapify(heap)
# heap = [1,2,4,3,6,8,9]

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heapq.heappush(heap, 2)
heapq.heappop(heap)

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A = []
A.append(1)
A.pop() #栈！
A.pop(0) #队列！

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a = collections.deque()
a.append(b)  #右边进（正常）
a.appendleft(c) #左边进
a.pop() #右边出（类似栈）
a.popleft() #左边进（类似队列） 

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intervals.sort(key=lambda x: x[0])

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for i, num in enumerate(nums,start = 0) #start默认从0开始

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from sortedcontainers import SortedSet
a = SortedSet()
self.cs = defaultdict(SortedSet) 
cs[0].add(1,'tiger')
cs[0].remove(1,'tiger')

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from collections import Counter
a = [1, 2, 1, 1, 4]
r = Counter(a)
#也可以统计字符串里的字符个数！
b = '124122'
r2 = Counter(b)
# 遍历法一：
for cnt in r.values():
	print(cnt)
#遍历法二：
for i, j in r.items():
	print(j)

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from sympy.ntheory.factor_ import digits
a = 12311
digits(a,b=10)

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n = int(input())                    # 棋盘nxn
x1, y1 = map(int, input().split())  # 
B = list(map(int, input().split()))  # 输入数组

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print(round(1.234, 2))
a = 1.1
print("%.2f"%a)

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import math
res = math.gcd(12,3)

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def gcd(x, y):
	return gcd(b, a%b) if b > 0 else a;
def lcm(x, y):
	if (x == 0): return y
	if (y == 0): return x
	return x * y / gcd(x, y)

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import functools
@functools.lru_cache(None)