gcd

Many problems require a GCD function so here it is. Greatest Common Divisor Stolen from https://github.com/pkorobeinikov/golang-example/edit/master/math/gcd.go

// GCDEuclidean calculates GCD by Euclidian algorithm.
func GCDEuclidean(a, b int) int {
    for a != b {
        if a > b {
            a -= b
        } else {
            b -= a
        }
    }

    return a
}

// GCDRemainderRecursive calculates GCD recursively using remainder.
func GCDRemainderRecursive(a, b int) int {
    if b == 0 {
        return a
    }
    return GCDRemainderRecursive(b, a%b)
}

// GCDRemainder calculates GCD iteratively using remainder.
func GCDRemainder(a, b int) int {
    for b != 0 {
        a, b = b, a%b
    }

    return a
}