Great GCD - great common denominator

GreatGCD_fCodeLab.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace facebookCodelab_greatGCD
{
    class Program
    {
        static void Main(string[] args)
        {
        }
    }


    /*
     * July 6, 2016 
     * Given 2 non negative integers m and n, find gcd(m, n)

GCD of 2 integers m and n is defined as the greatest integer g such that g is a divisor of both m and n.
Both m and n fit in a 32 bit signed integer.

Example

m : 6
n : 9

GCD(m, n) : 3 
NOTE : DO NOT USE LIBRARY FUNCTIONS
     * 
     * 
    */
    public class Solution
    {
        public int gcd(int a, int b)
        {
            if (a == b)
                return a;
            if (a < b)
            {
                int tmp = a;
                a = b;
                b = tmp;
            }

            if (b == 0)     // bug001 - forget to check if(b==0) first writing, not reaching facebook coding requirement! 
                return a;

            if (a % b == 0)
                return b;
            else
            {
                return gcd(a - b, b);
            }

        }
    }


}