Sheet 2 (Functions) - Q1 (OCD Edition)

/* A. Write a function to calculate factorial of any number, then write a
program to calculate a! + b! - c! using:
• Loop */
/* 5! = 5x4x3x2x1, 3! = 3x2x1
2! = 2x1, 0! - 1! = 1, n<0 = no factorial*/
#include <iostream>
using namespace std;

int loop_factorial (int n)
{
    int fact = 1; //n = 3
    for (int k = n ; k >= 1 ; k--)
    {
        fact *= k; 
        //or fact = fact * k;
    }
    if (n == 0)
        return 1;
    else
        return fact;
}

//• Recursion (without loops)
int rec_factorial (int n)
{
    if (n == 0 || n == 1)
        return 1;
    else
        return n * rec_factorial(n-1);
}

int main()
{
    int a, b, c, res;
    do
    {
        cout << "Please enter a: " << endl;
        cin >> a;
    } while (a < 0);
        do
    {
        cout << "Please enter b: " << endl;
        cin >> b;
    } while (b < 0);
        do
    {
        cout << "Please enter c: " << endl;
        cin >> c;
    } while (c < 0);
    res = rec_factorial(a) + rec_factorial (b) - rec_factorial(c);
    cout << "Result = " << res;
}