如何使用C++将字符从字符串转换为整数变量

#include <iostream>
#include <string>

int main() {
    std::string str = "123";
    int num1 = std::stoi(str);  // 使用stoi()函数
    int num2 = atoi(str.c_str());  // 使用atoi()函数

    std::cout << "num1: " << num1 << std::endl;
    std::cout << "num2: " << num2 << std::endl;

    return 0;
}

#include <iostream>
#include <sstream>

int main() {
    std::string str = "123";
    std::stringstream ss(str);
    int num;
    ss >> num;

    std::cout << "num: " << num << std::endl;

    return 0;
}

#include <iostream>
#include <string>

int main() {
    std::string str = "123";
    int num = std::stoi(str);

    std::cout << "num: " << num << std::endl;

    return 0;
}