Greatest Common Divisor.swift

//: [Palindrome](@previous)
/*:
 # Thursday Stretch Problem 5.4
 ## Greatest Common Divisor
 ### Instructions
 - Read about recursion.
 - Note Google's little joke when you search recursion in Chrome.
 - Create a function that returns the greatest common divisor of two numbers using recursion. (function calling itself).
 */

import Foundation

func greatestCommonDivisor(biggerNumber lhs: Int, smallerNumber rhs: Int) -> Int {
    if rhs <= 0 || lhs <= 0 {
        return 1
    } else if lhs % rhs == 0 {
        return rhs
    } else {
        print("\(rhs), \(lhs % rhs)")
        return greatestCommonDivisor(biggerNumber: rhs, smallerNumber: lhs % rhs )
    }
}

greatestCommonDivisor(biggerNumber: 20, smallerNumber: 15)
greatestCommonDivisor(biggerNumber: 20, smallerNumber: 0)
greatestCommonDivisor(biggerNumber: 1024, smallerNumber: 18)
greatestCommonDivisor(biggerNumber: 100, smallerNumber: 13)

// Euclid was a genius!