【C++ 】string类常见用法总结，超有用，算法竞赛必备

1
2
#include<string>

1
2
3
4
5
6
7
8
string s1;
// si = ""
string s2("Hello"); // s2 = "Hello"
string s3(4, 'K');
// s3 = "KKKK"
string s4("12345", 1, 3);
//s4 = "234"，即 "12345" 的从下标 1 开始，长度为 3 的子串

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
string s1, s2, s3;
s1 = "Hello";
// s1 = "Hello"
s2 = 'K';
// s2 = "K”
cin >> s3;
//s3从标准输入得到
tring s1("12345"), s2;
s3.assign(s1);
// s3 = s1
s2.assign(s1, 1, 2);
// s2 = "23"，即 s1 的子串(1, 2)
s2.assign(4, 'K');
// s2 = "KKKK"
s2.assign("abcde", 2, 3);
// s2 = "cde"，即 "abcde" 的下标 2 开始，长度为 3 的子串

1
2
3
4
string str;
const char *s = "qwert";
str=s //直接转化

1
2
3
4
5
6
char *p;
string str = "aqwea";
p = str.c_str();
//或者
p = str.data();

1
2
str.sizeof();

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
#include <string>
#include <sstream>
// 包含头文件
int main()
{
std::stringstream str2digit;
std::string sint='1', sfloat='1.1', sdouble='1.2';
int dint;
float dfloat;
double ddouble;
str2digit << sint; str2digit >> dint;
// string to int
str2digit.clear();
str2digit << sfloat; str2digit >> dfloat;
// string to float
str2digit.clear();
str2digit << sdouble; str2digit >> ddouble;
// string to double
std::cout << dint << ", " << dfloat << ", " << ddouble << std::endl;
return 0;
}
//本代码来源：知乎
//作者：赵剑行
//链接：https://www.zhihu.com/question/355533269/answer/1379154630

1
2
3
4
5
6
7
string a="123";
1.在字符串末尾添加一个字符
a.push_back('3'); //结果为 a="1233";
2.在字符串末尾删除一个字符
string a="123";
a.pop_back(); //结果为 a="12";

1
2
3
4
5
6
string s1 = "this is ok";
string s2 = s1.substr(2, 4);
// s2 = "is i"
s2 = s1.substr(2);
// s2 = "is is ok"

1
2
3
4
string s1("West”), s2("East");
s1.swap(s2);
// s1 = "East"，s2 = "West"

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
#include <iostream>
#include <string>
using namespace std;
int main()
{
string s1("Source Code");
int n;
if ((n = s1.find('u')) != string::npos) //查找 u 出现的位置
cout << "1) " << n << "," << s1.substr(n) << endl;
//输出 l)2,urce Code
if ((n = s1.find("Source", 3)) == string::npos)
//从下标3开始查找"Source"，找不到
cout << "2) " << "Not Found" << endl;
//输出 2) Not Found
if ((n = s1.find("Co")) != string::npos)
//查找子串"Co"。能找到，返回"Co"的位置
cout << "3) " << n << ", " << s1.substr(n) << endl;
//输出 3) 7, Code
if ((n = s1.find_first_of("ceo")) != string::npos)
//查找第一次出现或 'c'、'e'或'o'的位置
cout << "4) " << n << ", " << s1.substr(n) << endl;
//输出 4) l, ource Code
if ((n = s1.find_last_of('e')) != string::npos)
//查找最后一个 'e' 的位置
cout << "5) " << n << ", " << s1.substr(n) << endl;
//输出 5) 10, e
if ((n = s1.find_first_not_of("eou", 1)) != string::npos)
//从下标1开始查找第一次出现非 'e'、'o' 或 'u' 字符的位置
cout << "6) " << n << ", " << s1.substr(n) << endl;
//输出 6) 3, rce Code
return 0;
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
string s1("Real Steel");
s1.replace(1, 3, "123456", 2, 4);
//用 "123456" 的子串(2,4) 替换 s1 的子串(1,3)
cout << s1 << endl;
//输出 R3456 Steel
string s2("Harry Potter");
s2.replace(2, 3, 5, '0');
//用 5 个 '0' 替换子串(2,3)
cout << s2 << endl;
//输出 HaOOOOO Potter
int n = s2.find("OOOOO");
//查找子串 "00000" 的位置，n=2
s2.replace(n, 5, "XXX");
//将子串(n,5)替换为"XXX"
cout << s2 < < endl;
//输出 HaXXX Potter

1
2
3
4
5
6
string s1("Real Steel");
s1.erase(1, 3);
//删除子串(1, 3)，此后 s1 = "R Steel"
s1.erase(5);
//删除下标5及其后面的所有字符，此后 s1 = "R Ste"

1
2
3
4
5
6
7
8
string s1("Limitless"), s2("00");
s1.insert(2, "123");
//在下标 2 处插入字符串"123"，s1 = "Li123mitless"
s1.insert(3, s2);
//在下标 3 处插入 s2 , s1 = "Li10023mitless"
s1.insert(3, 5, 'X');
//在下标 3 处插入 5 个 'X'，s1 = "Li1XXXXX0023mitless"