implement next permutation

permutation.go

@@ -0,0 +1,29 @@
+package funk
+
+import "errors"
+
+// NextPermutation Implement next permutation,
+// which rearranges numbers into the lexicographically next greater permutation of numbers.
+func NextPermutation(nums []int) error {
+ n := len(nums)
+ if n == 0 {
+ return errors.New("nums is empty")
+ }
+
+ i := n - 2
+
+ for i >= 0 && nums[i] >= nums[i+1] {
+ i--
+ }
+
+ if i >= 0 {
+ j := n - 1
+ for j >= 0 && nums[i] >= nums[j] {
+ j--
+ }
+ nums[i], nums[j] = nums[j], nums[i]
+ }
+
+ ReverseInt(nums[i+1:])
+ return nil
+}

permutation_test.go

@@ -0,0 +1,34 @@
+package funk
+
+import (
+ "fmt"
+ "testing"
+)
+
+func TestNextPermutation(t *testing.T) {
+ type args struct {
+ nums []int
+ }
+ tests := []struct {
+ name string
+ args args
+ wantErr bool
+ }{
+ {
+ name: "case1",
+ args: args{
+ nums: []int{1, 2, 3},
+ },
+ wantErr: false,
+ },
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ if err := NextPermutation(tt.args.nums); (err != nil) != tt.wantErr {
+ t.Errorf("NextPermutation() error = %v, wantErr %v", err, tt.wantErr)
+ } else {
+ fmt.Println(tt.args.nums)
+ }
+ })
+ }
+}