add leetcode 46

Author: lijinglin3

leetcode/0046.permutations/permutations.go

@@ -0,0 +1,30 @@
+package leetcode
+
+var result [][]int
+
+func permute(nums []int) [][]int {
+	result = make([][]int, 0)
+	pathNums := make([]int, 0)
+	used := make([]bool, len(nums))
+	backtrack(nums, pathNums, used)
+	return result
+}
+
+func backtrack(nums, pathNums []int, used []bool) {
+	if len(nums) == len(pathNums) {
+		tmp := make([]int, len(nums))
+		copy(tmp, pathNums)
+		result = append(result, tmp)
+		return
+	}
+
+	for i := 0; i < len(nums); i++ {
+		if !used[i] {
+			used[i] = true
+			pathNums = append(pathNums, nums[i])
+			backtrack(nums, pathNums, used)
+			pathNums = pathNums[:len(pathNums)-1]
+			used[i] = false
+		}
+	}
+}

leetcode/0046.permutations/permutations_test.go

@@ -0,0 +1,18 @@
+package leetcode
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPermute(t *testing.T) {
+	assert.Equal(t, [][]int{
+		{1, 2, 3},
+		{1, 3, 2},
+		{2, 1, 3},
+		{2, 3, 1},
+		{3, 1, 2},
+		{3, 2, 1},
+	}, permute([]int{1, 2, 3}))
+}