6.30 C++ How to Program (8th Edition) By Paul Deitel, Harvey Deitel

(Reverse Digits) Write a function that takes an integer value and returns the number with its digits reversed. For example, given the number 7631, the function should return 1367.

Solution:

 
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
 
#include <cmath>
 
int reverse(int);
 
int main()
{
   int i;
 
   cout << "Enter integer: ";
   cin >> i;
   cout << "Reversed digits: " << reverse(i);
 
   return 0;
}
 
// reverse function
int reverse (int i)
{
   int digitsCount = 0;
 
   for(int digits = 1; digits <= i; digits *= 10)
   {
      digitsCount++;
   }
   int x = 0;
   int a = digitsCount;
 
   for(int j = 1; j <= digitsCount; j++)
   {
      a--;
      x += (i % 10) * pow(10, a);
      i = i / 10;
 
   }
   return x;
}