编辑代码

#include <iostream>
#include <sstream>
using namespace std;

int main() {
    double d_num;
    int i_num;
    string str;
    stringstream ss;

    // string -> double
    str = "123.3456789";
    ss << str;
    ss >> d_num;
    cout << "d_num: " << d_num << endl;

    // string -> int
    str = "654321";
    ss.clear();
    ss << str;
    ss >> i_num;
    cout << "i_num: " << i_num << endl;

	return 0;
}