diff --git a/top-100-liked/56/leetcode_test.go b/top-100-liked/56/leetcode_test.go
new file mode 100644
index 0000000..79bf93b
--- /dev/null
+++ b/top-100-liked/56/leetcode_test.go
@@ -0,0 +1,34 @@
+package top100liked
+
+import (
+	"fmt"
+	"testing"
+)
+
+// https://leetcode.cn/problems/subsets/?envType=study-plan-v2&envId=top-100-liked
+
+func subsets(nums []int) [][]int {
+	res := [][]int{{}}
+	var helper func(nums []int, length int, start int, r []int)
+	helper = func(nums []int, length int, start int, r []int) {
+		if len(r) == length {
+			cp := make([]int, length)
+			copy(cp, r)
+			res = append(res, cp)
+			return
+		}
+		for i := start; i < len(nums); i++ {
+			r = append(r, nums[i])
+			helper(nums, length, i+1, r)
+			r = r[:len(r)-1]
+		}
+	}
+	for i := range len(nums) {
+		helper(nums, i+1, 0, []int{})
+	}
+	return res
+}
+
+func Test(t *testing.T) {
+	fmt.Printf("%+v", subsets([]int{1, 2, 3}))
+}
diff --git a/top-100-liked/57/leetcode_test.go b/top-100-liked/57/leetcode_test.go
new file mode 100644
index 0000000..deca425
--- /dev/null
+++ b/top-100-liked/57/leetcode_test.go
@@ -0,0 +1,44 @@
+package top100liked
+
+import (
+	"fmt"
+	"testing"
+)
+
+// https://leetcode.cn/problems/letter-combinations-of-a-phone-number?envType=study-plan-v2&envId=top-100-liked
+
+var m = map[byte][]byte{
+	'2': []byte("abc"),
+	'3': []byte("def"),
+	'4': []byte("ghi"),
+	'5': []byte("jkl"),
+	'6': []byte("mno"),
+	'7': []byte("pqrs"),
+	'8': []byte("tuv"),
+	'9': []byte("wxyz"),
+}
+
+func letterCombinations(digits string) []string {
+	res := []string{}
+
+	var helper func(idx int, r []byte)
+	helper = func(idx int, r []byte) {
+		if idx == len(digits) {
+			res = append(res, string(r))
+			return
+		}
+		for j := range m[digits[idx]] {
+			r = append(r, m[digits[idx]][j])
+			helper(idx+1, r)
+			r = r[:len(r)-1]
+		}
+	}
+
+	helper(0, []byte{})
+	return res
+}
+
+func Test(t *testing.T) {
+	fmt.Printf("%+v", letterCombinations("23"))
+	fmt.Printf("%+v", letterCombinations("2"))
+}