Greatest Common Divisor

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.

m : 6
n : 9

GCD(m, n) : 3 

Solution:

Time: O(log A)
Space: O(1)

public class Solution {
    public int gcd(int A, int B) {
        if (B == 0) return A;
        return gcd(B, A % B);
    }
}