string类型转换int类型

C++转换形式(C++11):

int main(int argc, char* argv[])
{    
    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);
    // error: 'std::invalid_argument'
     /*int myint4 = std::stoi(str4);*/

    std::cout << "std::stoi("" << str1 << "") is " << myint1 << '
';
    std::cout << "std::stoi("" << str2 << "") is " << myint2 << '
';
    std::cout << "std::stoi("" << str3 << "") is " << myint3 << '
';
    /*std::cout << "std::stoi("" << str4 << "") is " << myint4 << '
';*/
}

output:

std::stoi("45") is 45
std::stoi("3.14159") is 3
std::stoi("31337 with words") is 31337

同样, 可以使用 stol(long), stof(float), stod(double) 等.