feat: add gcd problem

Author: codejsha

README.md

@@ -869,7 +869,7 @@ Math.abs(-34.5), Math.ceil(2.17), Math.floor(3.14), Math.max(x, -3), Math.min(x,
 
 - Combination: [c++](cpp-algorithm/src/math)(`GenerateCombination`) | Find the number of ways to choose $k$ items from $n$ items.
 - Fast Fourier transform: Fast Fourier transform is a mathematical algorithm that finds the discrete Fourier transform of a set of real numbers.
-- Greatest common divisor (GCD), CLRS#31.2: [python](python-algorithm/algorithm/math), [java](java-algorithm/src/main/java/com/example/algorithm/math) | Find the greatest common divisor of two numbers.
+- Greatest common divisor (GCD), CLRS#31.2: [python](python-algorithm/algorithm/math), [java](java-algorithm/src/main/java/com/example/algorithm/math), [go](go-algorithm/internal/math) | Find the greatest common divisor of two numbers.
 - Integer factorization: [c++](cpp-algorithm/src/math), [java](java-algorithm/src/main/java/com/example/algorithm/math) | Integer factorization is the process of determining which prime numbers divide a given positive integer.
 - Least common multiple (LCM): [python](python-algorithm/algorithm/math), [java](java-algorithm/src/main/java/com/example/algorithm/math) | Find the least common multiple of two numbers.
 - Miller-Rabin primality test, CLRS#31.8: [c++](cpp-algorithm/src/math) | Miller-Rabin primality test is a mathematical algorithm that finds whether a given number is prime.

go-algorithm/go.mod

@@ -1,3 +1,11 @@
 module go-algorithm
 
 go 1.22.4
+
+require github.com/stretchr/testify v1.9.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go-algorithm/go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

go-algorithm/internal/math/gcd.go

@@ -0,0 +1,9 @@
+package math
+
+// GCD returns the greatest common divisor of a(dividend) and b(divisor).
+func GCD(a int, b int) int {
+	for b != 0 {
+		a, b = b, a%b
+	}
+	return a
+}

go-algorithm/internal/math/gcd_test.go

@@ -0,0 +1,12 @@
+package math
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestGCD(t *testing.T) {
+	assert.Equal(t, 12, GCD(24, 36))
+	assert.Equal(t, 1, GCD(17, 22))
+	assert.Equal(t, 20, GCD(120, 500))
+}