Write program to calculate factorial of a number

 0! = 1

1! = 1

//Time complexity O(n) and Space complexity O(n)

int factorial_recursive(int n) {

    if(n < 0) {

         return 0;

    }

    if(n == 0) {

        return 1;

    }

    return factorial_recursive(n - 1) * n;

}   

//Time complexity O(n) and Space complexity O(1)

int factorial_iterative(int n) {

    if(n < 0) {

        return 0;

    }

    if(n == 0) {

        return 1;

    }

    int result = 1;

    for(int i = 1; i <= n; i++) {

        result *= i;

    }

    return result;

}