C++ int转string string转int 完美实现

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

int str2int(const string& word) {
    int Sum = 0;
    string temp = word;
    while (temp != "") {
        Sum *= 10;
        Sum += temp[0] - '0';
        temp = temp.substr(1);
    }
    return Sum;
}

string int2str(const int& num) {
    ostringstream out;  //#include <sstream>
    out << num;
    return out.str();
}

//==============test=================
int main() {
    cout<<int2str(100)<<endl;
    cout<<str2int("200")<<endl;

}