Factorial Using recursion

Factorial of number n (n!) is 1* 2 * ... (n-1) *  n
5! = 5*4*3*2*1 = 120

Checkout: Factorial without recursion

Solution: 
Recursion is the process in which functions calls itself until some base condition is met. Recursion helps in writing shorter functions by dividing a problem into small parts and then solving that problem using a same function again.

We know that n! = 1 for n = 0, n! = n * (n-1)!  for n > 0
For writing a recursive method we can use base condition when n become 1 and call the recursive method with (n-1) at each call.

#include<stdio.h>

int factorial(int n) {
     if(n>0) {
           return n * factorial(n-1);
     }
     else {
           return 1;
     }
}

int main()
{
    int num =5;
    printf("Factorial of %d : %d", num, factorial(num));
}

Output:

Factorial of 5 : 120