feat: add Shuffle

slice.go

@@ -9,6 +9,8 @@ package lol
 import (
 	"golang.org/x/exp/constraints"
 	"golang.org/x/exp/slices"
+	"math/rand"
+	"time"
 )
 
 // SortSlice sorts a slice. Just a wrapper for slices.Sort.
@@ -154,7 +156,7 @@ func Map[T any](list []T, fn func(v T) T) []T {
 	return list
 }
 
-// MapTo is same as Map, but it can return another type slice.
+// MapTo is same as Map, but it can return another type of slice.
 //
 // Special case: when fn is nil, it returns the empty slice.
 //
@@ -175,6 +177,19 @@ func MapTo[T any, R any](list []T, fn func(v T) R) []R {
 	return res
 }
 
+// Shuffle shuffles a slice for random order.
+// Implement based on rand.Shuffle
+//
+// Play: https://go.dev/play/p/A2yeiJDWIHp
+func Shuffle[T any](list []T) {
+	if len(list) == 0 {
+		return
+	}
+	s := rand.NewSource(time.Now().UnixNano())
+	rand.New(s).Shuffle(len(list), func(i, j int) { list[i], list[j] = list[j], list[i] })
+	return
+}
+
 // Reduce accumulates and combines elements through a fn into a single value.
 //
 // Special case: when fn is nil, it returns the initial value

slice_example_test.go

@@ -88,6 +88,12 @@ func ExampleMapTo() {
 	// [Heisenberg Hank Saul]
 }
 
+func ExampleShuffle() {
+	s := []string{"a", "b", "c", "d"}
+	Shuffle(s)
+	fmt.Println(s)
+}
+
 func ExampleReduce() {
 	res1 := Reduce([]int{1, 7, 3, 4}, func(s float64, v, i int) float64 {
 		return s * float64(v)

slice_test.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"github.com/stretchr/testify/assert"
 	"sort"
+	"strings"
 	"testing"
 )
 
@@ -155,6 +156,15 @@ func TestMapTo(t *testing.T) {
 	assert.Equalf(t, []string{"Heisenberg", "Hank", "Saul"}, got, "extract struct")
 }
 
+func TestShuffle(t *testing.T) {
+	s := []string{"a", "b", "c", "d", "e", "a", "b", "c", "d", "e", "a", "b", "c", "d", "e", "a", "b", "c", "d", "e"}
+	s1 := strings.Join(s, "")
+	Shuffle(s)
+	s2 := strings.Join(s, "")
+	// Probabilistic problem
+	assert.NotEqualf(t, s1, s2, "shuffle string")
+}
+
 func TestReduce(t *testing.T) {
 	t.Parallel()