Question

1. In ANSII standard C++, there is no library function to convert an 
integer to a string. Your program should develop such a 
function. In other words complete the following program using your 
itos function. (Use of other C functions is prohibitted)

// this program will read in an integer and convert it to a string

#include <iostream>
#include <cstdlib>
#include <string>

using namespace std;

string itos(int n) {
}


int main(int argc, char* argv[]){
        int n = atoi(argv[1]);
        cout << "file "+ itos(n)+ " .txt" << endl;
        return 0;
}

Answer 1

#include <iostream>
#include <cstdlib>
#include <string>

using namespace std;

string itos(int n) {
    if (n == 0) {
        return "0";
    } else {
        string s;
        if (n < 0) {
            s += "-";
            n = -n;
        }
        while (n > 0) {
            int d = n % 10;
            n /= 10;
            s += (char)(d+'0');
        }
        char temp;
        for (int i = 0; i < s.length() / 2; ++i) {
            temp = s[i];
            s[i] = s[s.length()-i-1];
            s[s.length()-i-1] = temp;
        }
        return s;
    }
}

int main(int argc, char* argv[]){
    int n = atoi(argv[1]);
    cout << "file "+ itos(n)+ " .txt" << endl;
    return 0;
}