Merge pull request thoas#103 from CengSin/feature_numbers_permutation

implement numbers permutation

Author: thoas

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)
+			}
+		})
+	}
+}