reverse_integer.c

/*

    reverse_integer.c

https://www.programmingsimplified.com/c/source-code/c-program-reverse-number
https://www.geeksforgeeks.org/write-a-program-to-reverse-digits-of-a-number/


    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

#include <stdio.h>

int reverse_v1(int num)
{
    int rev_num = 0;

    while(num > 0)
    {
        rev_num = rev_num*10 + num%10;
        num = num/10;
    }

    return rev_num;
}

int reverse_by_recursion_v1(int num, int rev)
{
    if(num==0)
        return rev;
    else
        return reverse_by_recursion_v1(num/10, rev*10 + num%10);
}

long reverse_by_recursion_v2(long n) {
   static long r = 0;

   if (n == 0)
      return 0;

   r = r * 10;
   r = r + n % 10;
   reverse_by_recursion_v2(n/10);

   return r;
}

int main(void)
{
    int number, reversed_number;

    printf("\n Enter integer: ");
    scanf("%d", &number);

    reversed_number = reverse_v1(number);
    printf("\n\n\t reverse_v1(number) \n");
    printf("\n Reverse of %d  is  %d \n", number, reversed_number);

    // reverse by recursion v1
    // Second argument must be 0 while calling function
    printf("\n\n\t reverse_by_recursion(number, 0) \n");
    reversed_number = reverse_by_recursion_v1(number, 0);
    printf("\n Reverse of %d  is  %d \n", number, reversed_number);

    // reverse by recursion v2
    printf("\n\n\t reverse_by_recursion_v2(number) \n");
    reversed_number = reverse_by_recursion_v2(number);
    printf("\n Reverse of %d  is  %d \n\n", number, reversed_number);

    return 0;

} // main()