认识达内从这里开始

一、string 转 int

1、atoi

string s = "-1234";

cout <<"atoi(s.c_str()): " << atoi(s.c_str()) << endl;

cout << typeid(atoi(s.c_str())).name() << endl;

2、strtol

ong int strtol (const charstr, char* endptr, int base);

str 为要转换的字符串，endstr 为第一个不能转换的字符的指针，base 为字符串 str 所采用的进制。

int x = 0;

string str1 = "100";

string str2 = "-100";

string str3 = "100a";

x = strtol(str1.c_str(), nullptr, 10);

cout << x << endl;

x = strtol(str2.c_str(), nullptr, 10);

cout << x << endl;

x = strtol(str3.c_str(), nullptr, 10);

cout << x << endl;

3、stoi c++11之后才引入，需要引入 <string> 头文件

int x = 0;

string str1 = "100";

string str2 = "-100";

string str3 = "100a";

x = stoi(str1);

cout << x << endl;

x = stoi(str2);

cout << x << endl;

x = stoi(str3);

cout << x << endl;

4、stringstream 需要引入<sstream> 头文件

int stringToInt(const string& s)

{

stringstream ss;

int result;

ss << s;

ss >> result;

return result;

}

int main()

{

string str1 = "100";

string str2 = "-100";

string str3 = "100a";

cout << stringToInt(str1) << endl;

cout << stringToInt(str2) << endl;

cout << stringToInt(str3) << endl;

}

二、int 转 string

1、sprintf_s

int number = 100;

char buff[128] = { 0 };

sprintf_s(buff, 128, "%d", number);

cout << buff << endl;

2、stringstream

需引入该<stringstream>头文件

int number = 100;

stringstream ss;

ss << number;

string str = ss.str();

cout << str << endl;

3、to_string()

c++11 后的新特性，需要引入<string> 头文件

int number = 100;

string str = to_string(number);

cout << str << endl;