From 654ba15aaffd4e8610fdc0aeb1cd4c1a61b81b3c Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Sat, 6 May 2023 11:02:00 +0800
Subject: [PATCH] feat: add GCD and LCM function

---
 mathutil/mathutil.go      | 42 +++++++++++++++++++++++++++++++++++++++
 mathutil/mathutil_test.go | 38 +++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/mathutil/mathutil.go b/mathutil/mathutil.go
index c97967c..d76303b 100644
--- a/mathutil/mathutil.go
+++ b/mathutil/mathutil.go
@@ -256,3 +256,45 @@ func IsPrime(n int) bool {
 
 	return true
 }
+
+// GCD return greatest common divisor (GCD) of integers.
+// Play: todo
+func GCD[T constraints.Integer](integers ...T) T {
+	result := integers[0]
+
+	for k := range integers {
+		result = gcd(integers[k], result)
+
+		if result == 1 {
+			return 1
+		}
+	}
+
+	return result
+}
+
+// find greatest common divisor (GCD)
+func gcd[T constraints.Integer](a, b T) T {
+	if b == 0 {
+		return a
+	}
+
+	return gcd(b, a%b)
+}
+
+// LCM return Least Common Multiple (LCM) of integers.
+// Play: todo
+func LCM[T constraints.Integer](integers ...T) T {
+	result := integers[0]
+
+	for i := 1; i < len(integers)-1; i++ {
+		result = lcm(result, integers[i])
+	}
+
+	return result
+}
+
+// find Least Common Multiple (LCM) via GCD.
+func lcm[T constraints.Integer](a, b T) T {
+	return a * b / gcd(a, b)
+}
diff --git a/mathutil/mathutil_test.go b/mathutil/mathutil_test.go
index 62bc390..319015f 100644
--- a/mathutil/mathutil_test.go
+++ b/mathutil/mathutil_test.go
@@ -210,3 +210,41 @@ func TestIsPrime(t *testing.T) {
 	assert.Equal(true, IsPrime(3))
 	assert.Equal(false, IsPrime(4))
 }
+
+func TestGCD(t *testing.T) {
+	assert := internal.NewAssert(t, "TestGCD")
+
+	assert.Equal(1, GCD(1, 1))
+	assert.Equal(1, GCD(1, -1))
+	assert.Equal(-1, GCD(-1, 1))
+	assert.Equal(-1, GCD(-1, -1))
+
+	assert.Equal(1, GCD(1, 0))
+	assert.Equal(1, GCD(0, 1))
+	assert.Equal(-1, GCD(-1, 0))
+	assert.Equal(-1, GCD(0, -1))
+
+	assert.Equal(1, GCD(1, -2))
+	assert.Equal(1, GCD(-2, 1))
+	assert.Equal(-1, GCD(-1, 2))
+	assert.Equal(-1, GCD(2, -1))
+
+	assert.Equal(-1, GCD(-1, -2))
+	assert.Equal(-1, GCD(-2, -1))
+
+	assert.Equal(-9, GCD(-27, -36))
+	assert.Equal(3, GCD(3, 6, 9))
+}
+
+func TestLCM(t *testing.T) {
+	assert := internal.NewAssert(t, "TestLCM")
+
+	assert.Equal(0, LCM(0))
+	assert.Equal(1, LCM(1))
+	assert.Equal(-1, LCM(-1))
+	assert.Equal(0, LCM(0, -1))
+	assert.Equal(0, LCM(0, 1))
+	assert.Equal(1, LCM(1, 1))
+	assert.Equal(1, LCM(1, 2))
+	assert.Equal(6, LCM(3, 6, 9))
+}