diff --git a/solution/0000-0099/0017.Letter Combinations of a Phone Number/README.md b/solution/0000-0099/0017.Letter Combinations of a Phone Number/README.md
index 58d325892108f..bd6f35a246a46 100644
--- a/solution/0000-0099/0017.Letter Combinations of a Phone Number/README.md	
+++ b/solution/0000-0099/0017.Letter Combinations of a Phone Number/README.md	
@@ -392,25 +392,27 @@ func letterCombinations(digits string) (ans []string) {
 
 ```ts
 function letterCombinations(digits: string): string[] {
-    if (digits.length == 0) {
+    if (digits.length === 0) {
         return [];
     }
     const ans: string[] = [];
-    const t: string[] = [];
-    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'];
-    const dfs = (i: number) => {
-        if (i >= digits.length) {
-            ans.push(t.join(''));
+    const n = digits.length;
+    const d: string[][] = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'].map(x => [
+        ...x,
+    ]);
+
+    const dfs = (curr: string, start: number) => {
+        if (curr.length === n) {
+            ans.push(curr);
             return;
         }
-        const s = d[parseInt(digits[i]) - 2];
-        for (const c of s) {
-            t.push(c);
-            dfs(i + 1);
-            t.pop();
+        for (let i = start; i < n; i++) {
+            for (const ch of d[+digits[i] - 2]) {
+                dfs(curr + ch, i + 1);
+            }
         }
     };
-    dfs(0);
+    dfs('', 0);
     return ans;
 }
 ```
@@ -453,25 +455,25 @@ impl Solution {
  * @return {string[]}
  */
 var letterCombinations = function (digits) {
-    if (digits.length == 0) {
+    if (digits.length === 0) {
         return [];
     }
     const ans = [];
-    const t = [];
-    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'];
-    const dfs = i => {
-        if (i >= digits.length) {
-            ans.push(t.join(''));
+    const n = digits.length;
+    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'].map(x => [...x]);
+
+    const dfs = (curr, start) => {
+        if (curr.length === n) {
+            ans.push(curr);
             return;
         }
-        const s = d[parseInt(digits[i]) - 2];
-        for (const c of s) {
-            t.push(c);
-            dfs(i + 1);
-            t.pop();
+        for (let i = start; i < n; i++) {
+            for (const ch of map[+digits[i] - 2]) {
+                dfs(curr + ch, i + 1);
+            }
         }
     };
-    dfs(0);
+    dfs('', 0);
     return ans;
 };
 ```
diff --git a/solution/0000-0099/0017.Letter Combinations of a Phone Number/README_EN.md b/solution/0000-0099/0017.Letter Combinations of a Phone Number/README_EN.md
index a15369a5b20c5..407b70a120d52 100644
--- a/solution/0000-0099/0017.Letter Combinations of a Phone Number/README_EN.md	
+++ b/solution/0000-0099/0017.Letter Combinations of a Phone Number/README_EN.md	
@@ -388,25 +388,27 @@ func letterCombinations(digits string) (ans []string) {
 
 ```ts
 function letterCombinations(digits: string): string[] {
-    if (digits.length == 0) {
+    if (digits.length === 0) {
         return [];
     }
     const ans: string[] = [];
-    const t: string[] = [];
-    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'];
-    const dfs = (i: number) => {
-        if (i >= digits.length) {
-            ans.push(t.join(''));
+    const n = digits.length;
+    const d: string[][] = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'].map(x => [
+        ...x,
+    ]);
+
+    const dfs = (curr: string, start: number) => {
+        if (curr.length === n) {
+            ans.push(curr);
             return;
         }
-        const s = d[parseInt(digits[i]) - 2];
-        for (const c of s) {
-            t.push(c);
-            dfs(i + 1);
-            t.pop();
+        for (let i = start; i < n; i++) {
+            for (const ch of d[+digits[i] - 2]) {
+                dfs(curr + ch, i + 1);
+            }
         }
     };
-    dfs(0);
+    dfs('', 0);
     return ans;
 }
 ```
@@ -449,25 +451,25 @@ impl Solution {
  * @return {string[]}
  */
 var letterCombinations = function (digits) {
-    if (digits.length == 0) {
+    if (digits.length === 0) {
         return [];
     }
     const ans = [];
-    const t = [];
-    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'];
-    const dfs = i => {
-        if (i >= digits.length) {
-            ans.push(t.join(''));
+    const n = digits.length;
+    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'].map(x => [...x]);
+
+    const dfs = (curr, start) => {
+        if (curr.length === n) {
+            ans.push(curr);
             return;
         }
-        const s = d[parseInt(digits[i]) - 2];
-        for (const c of s) {
-            t.push(c);
-            dfs(i + 1);
-            t.pop();
+        for (let i = start; i < n; i++) {
+            for (const ch of map[+digits[i] - 2]) {
+                dfs(curr + ch, i + 1);
+            }
         }
     };
-    dfs(0);
+    dfs('', 0);
     return ans;
 };
 ```
diff --git a/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.js b/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.js
index 3ba4721ef1457..480c6f03e4ee6 100644
--- a/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.js	
+++ b/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.js	
@@ -3,24 +3,24 @@
  * @return {string[]}
  */
 var letterCombinations = function (digits) {
-    if (digits.length == 0) {
+    if (digits.length === 0) {
         return [];
     }
     const ans = [];
-    const t = [];
-    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'];
-    const dfs = i => {
-        if (i >= digits.length) {
-            ans.push(t.join(''));
+    const n = digits.length;
+    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'].map(x => [...x]);
+
+    const dfs = (curr, start) => {
+        if (curr.length === n) {
+            ans.push(curr);
             return;
         }
-        const s = d[parseInt(digits[i]) - 2];
-        for (const c of s) {
-            t.push(c);
-            dfs(i + 1);
-            t.pop();
+        for (let i = start; i < n; i++) {
+            for (const ch of map[+digits[i] - 2]) {
+                dfs(curr + ch, i + 1);
+            }
         }
     };
-    dfs(0);
+    dfs('', 0);
     return ans;
 };
diff --git a/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.ts b/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.ts
index 3c6dce34cf09c..34e4bc83d9846 100644
--- a/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.ts	
+++ b/solution/0000-0099/0017.Letter Combinations of a Phone Number/Solution2.ts	
@@ -1,22 +1,24 @@
 function letterCombinations(digits: string): string[] {
-    if (digits.length == 0) {
+    if (digits.length === 0) {
         return [];
     }
     const ans: string[] = [];
-    const t: string[] = [];
-    const d = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'];
-    const dfs = (i: number) => {
-        if (i >= digits.length) {
-            ans.push(t.join(''));
+    const n = digits.length;
+    const d: string[][] = ['abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz'].map(x => [
+        ...x,
+    ]);
+
+    const dfs = (curr: string, start: number) => {
+        if (curr.length === n) {
+            ans.push(curr);
             return;
         }
-        const s = d[parseInt(digits[i]) - 2];
-        for (const c of s) {
-            t.push(c);
-            dfs(i + 1);
-            t.pop();
+        for (let i = start; i < n; i++) {
+            for (const ch of d[+digits[i] - 2]) {
+                dfs(curr + ch, i + 1);
+            }
         }
     };
-    dfs(0);
+    dfs('', 0);
     return ans;
 }