Merge branch 'feature/gcd' into develop

Author: codejsha

go-algorithm/internal/math/gcd.go

@@ -0,0 +1,28 @@
+package math
+
+type GCD interface {
+	gcd(a int, b int) int
+	gcdExtended(a int, b int) (int, int, int)
+}
+
+type NumberTuple struct {
+	a int // dividend
+	b int // divisor
+}
+
+// GCD finds the greatest common divisor of two numbers.
+func (n NumberTuple) gcd() int {
+	for n.b != 0 {
+		n.a, n.b = n.b, n.a%n.b
+	}
+	return n.a
+}
+
+// GCDExtended finds the greatest common divisor of two numbers with extended Euclidean algorithm.
+func (n NumberTuple) gcdExtended() (int, int, int) {
+	if n.b == 0 {
+		return n.a, 1, 0
+	}
+	d, x, y := NumberTuple{n.b, n.a % n.b}.gcdExtended()
+	return d, y, x - (n.a/n.b)*y
+}

go-algorithm/internal/math/gcd_test.go

@@ -0,0 +1,21 @@
+package math
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestGCD(t *testing.T) {
+	assert.Equal(t, 12, NumberTuple{24, 36}.gcd())
+	assert.Equal(t, 1, NumberTuple{17, 22}.gcd())
+	assert.Equal(t, 20, NumberTuple{120, 500}.gcd())
+}
+
+func TestGCDExtended(t *testing.T) {
+	d1, _, _ := NumberTuple{24, 36}.gcdExtended()
+	assert.Equal(t, 12, d1)
+	d2, _, _ := NumberTuple{17, 22}.gcdExtended()
+	assert.Equal(t, 1, d2)
+	d3, _, _ := NumberTuple{120, 500}.gcdExtended()
+	assert.Equal(t, 20, d3)
+}