The most efficient way to reverse a number

Question

I am looking for an efficient algorithm to reverse a number, e.g.

Input: 3456789

Output: 9876543

In C++ there are p

Answer 1

#include 
unsigned int reverse(unsigned int val)
{
 unsigned int retval = 0;

 while( val > 0)
 {
     retval  = 10*retval + val%10;
     val     /= 10;
 }
 printf("returning - %d", retval);
 return retval;
}


int main()
{
    reverse(123);
}