Question

I’ve written a small program in C++ that prompts the user for input, the user gives a number, then the computer displays the number reversed.

For example: 17 becomes 71. 123 becomes 321.

This is the program:

#include <iostream>
#include <string>  //for later use.
using namespace std;

int rev(int x)
{
    int r = 0;
    while(x)
    {
        r = (r*10) + (x%10);
        x = x/10;
    }
    return r;
}

int main()
{
    int nr;
    cout << "Give a number: ";
    cin >> nr;
    rev(nr);
    cout << nr; 
    return 0;
}

The final result of the program: prints the same number, function has no effect. What am I doing wrong? I tried several solutions but to no avail.

Answer 1

You need to change rev(nr); to nr = rev(nr);

or alternately change your function to:

void rev(int& x)
{
    int r = 0;
    while(x)
    {
        r = (r*10) + (x%10);
        x = x/10;
    }
    x = r;
}