Why does my code not handle negative numbers for reversing?

[JoshuaStudent]

My program takes an integer negative or positive and outputs the reverse. If the reverse overflows or underflows it returns 0.

#include <iostream>
#include <climits> 
#include <limits.h>
using namespace std;

/**
 * PURPOSE: displays reverse of the number or a 0 if it overflows. 
 * PARAMETERS:
 *     int 
 * RETURN VALUES:
 *     reverse of integer input. 
*/



int main() {
    int n, reverse = 0;
    bool invalid = false;
    
    cout << "Enter an integer: ";
    cin >> n;
     while(n ) {
        int oldVal = reverse;
        int remainder = n%10;
        reverse = reverse*10 + remainder;
        if (reverse < oldVal) {
            invalid = true;
            break;
            
        }
        n/=10;
    }
       if(invalid) 
       cout <<"0" << endl; 
       else 
       cout <<reverse << endl;
    
    return 0;
}

[Thomas1965]

When you enter -11 the value of reverse is -1 and oldVal is 0

if (reverse < oldVal) 
{
   invalid = true;
   break;
}

[JoshuaStudent]

I know it doesn't work. But how do I fix it.

[Moschops]

If it's negative, make it positive, find the reverse, and then make that negative.

I'm assuming that you want, for example, -91 to be reversed to -19.

[JoshuaStudent]

I changed it to something that works with negative or positive, but doesn't work for overflow. It does not return 0 on overflow like it's supposed to because I used a long.
#include <iostream>

using namespace std;

class Operations
{
long c;

public:
void inputNumber()
{
cout << "Input a number\n";
cin >> c;
}

long reverseNumber()
{
long invert = 0;

while (c != 0)
{
invert = invert * 10;
invert = invert + c%10;
c = c/10;
}

return invert;
}

};

int main()
{
long result;

Operations t;
t.inputNumber();
result = t.reverseNumber();

cout << "Number obtained on reversal = " << result << endl;

return 0;
}