C++string与int的相互转换（使用C++11）-白红宇

C++string与int的相互转换（使用C++11）

阅读量：4580 次

发布时间：2019-06-09

本文共 1988 字，大约阅读时间需要 6 分钟。

一、int转string

#include 
    
     #include 
     
       int main() {    double f = 23.43;    double f2 = 1e-9;    double f3 = 1e40;    double f4 = 1e-40;    double f5 = 123456789;    std::string f_str = std::to_string(f);    std::string f_str2 = std::to_string(f2); // 注意：返回 "0.000000"    std::string f_str3 = std::to_string(f3); // 注意：不返回 "1e+40".    std::string f_str4 = std::to_string(f4); // 注意：返回 "0.000000"    std::string f_str5 = std::to_string(f5);    std::cout << "std::cout: " << f << '\n'              << "to_string: " << f_str  << "\n\n"              << "std::cout: " << f2 << '\n'              << "to_string: " << f_str2 << "\n\n"              << "std::cout: " << f3 << '\n'              << "to_string: " << f_str3 << "\n\n"              << "std::cout: " << f4 << '\n'              << "to_string: " << f_str4 << "\n\n"              << "std::cout: " << f5 << '\n'              << "to_string: " << f_str5 << '\n';}

输出

std::cout: 23.43to_string: 23.430000 std::cout: 1e-09to_string: 0.000000 std::cout: 1e+40to_string: 10000000000000000303786028427003666890752.000000 std::cout: 1e-40to_string: 0.000000 std::cout: 1.23457e+08to_string: 123456789.000000

二、string转int

#include 
    
     #include 
     
       int main(){    std::string str1 = "45";    std::string str2 = "3.14159";    std::string str3 = "31337 with words";    std::string str4 = "words and 2";     int myint1 = std::stoi(str1);    int myint2 = std::stoi(str2);    int myint3 = std::stoi(str3);    // 错误： 'std::invalid_argument'    // int myint4 = std::stoi(str4);     std::cout << "std::stoi(\"" << str1 << "\") is " << myint1 << '\n';    std::cout << "std::stoi(\"" << str2 << "\") is " << myint2 << '\n';    std::cout << "std::stoi(\"" << str3 << "\") is " << myint3 << '\n';    //std::cout << "std::stoi(\"" << str4 << "\") is " << myint4 << '\n';}

结果：