commit solution 415

Author: lxlxw

Diff for: index-tags.md

@@ -48,6 +48,7 @@
 |  [125](https://leetcode-cn.com/problems/valid-palindrome)  |  [验证回文串](/solution/100-199/0125.valid-palindrome/)  |  `双指针`,`字符串`  |  <font color=green>简单</font>  |✅ |
 |  [344](https://leetcode-cn.com/problems/reverse-string)  |  [反转字符串](/solution/300-399/0344.reverse-string/)  |  `双指针`,`字符串`  |  <font color=green>简单</font>  |✅ |
 |  [345](https://leetcode-cn.com/problems/reverse-vowels-of-a-string)  |  [反转字符串中的元音字母](/solution/300-399/0345.reverse-vowels-of-a-string/)  |  `双指针`,`字符串`  |  <font color=green>简单</font>  |✅ |
+|  [415](https://leetcode-cn.com/problems/add-strings)  |  [字符串相加](/solution/400-499/0415.add-strings/)  |  `字符串`  |  <font color=green>简单</font>  |✅ |
 |  [557](https://leetcode-cn.com/problems/reverse-words-in-a-string-iii)  |  [反转字符串中的单词 iii](/solution/500-599/0557.reverse-words-in-a-string-iii/)  |  `字符串`  |  <font color=green>简单</font>  |✅ |
 
 #### **数学**

Diff for: index-type.md

@@ -120,7 +120,7 @@
 |  [409](https://leetcode-cn.com/problems/longest-palindrome)  |  [最长回文串](/solution/400-499/0409.longest-palindrome/)  |  `哈希表`  |  <font color=green>简单</font>  |✅ |
 |  [412](https://leetcode-cn.com/problems/fizz-buzz)  |  [fizz buzz](/solution/400-499/0412.fizz-buzz/)  |    |  <font color=green>简单</font>  |
 |  [414](https://leetcode-cn.com/problems/third-maximum-number)  |  [第三大的数](/solution/400-499/0414.third-maximum-number/)  |  `数组`  |  <font color=green>简单</font>  |✅ |
-|  [415](https://leetcode-cn.com/problems/add-strings)  |  [字符串相加](/solution/400-499/0415.add-strings/)  |  `字符串`  |  <font color=green>简单</font>  |
+|  [415](https://leetcode-cn.com/problems/add-strings)  |  [字符串相加](/solution/400-499/0415.add-strings/)  |  `字符串`  |  <font color=green>简单</font>  |✅ |
 |  [422](https://leetcode-cn.com/problems/valid-word-square)  |  [有效的单词方块](/solution/400-499/0422.valid-word-square/)  |    |  <font color=green>简单</font>  |
 |  [434](https://leetcode-cn.com/problems/number-of-segments-in-a-string)  |  [字符串中的单词数](/solution/400-499/0434.number-of-segments-in-a-string/)  |  `字符串`  |  <font color=green>简单</font>  |
 |  [437](https://leetcode-cn.com/problems/path-sum-iii)  |  [路径总和 iii](/solution/400-499/0437.path-sum-iii/)  |  `树`  |  <font color=green>简单</font>  |

Diff for: solution/400-499/_sidebar.md

@@ -21,7 +21,7 @@
     - [412. fizz buzz](solution/400-499/0412.fizz-buzz/)
     - [413. 等差数列划分](solution/400-499/0413.arithmetic-slices/)
     - [414. 第三大的数 ✅](solution/400-499/0414.third-maximum-number/)
-    - [415. 字符串相加](solution/400-499/0415.add-strings/)
+    - [415. 字符串相加 ✅](solution/400-499/0415.add-strings/)
     - [416. 分割等和子集](solution/400-499/0416.partition-equal-subset-sum/)
     - [417. 太平洋大西洋水流问题](solution/400-499/0417.pacific-atlantic-water-flow/)
     - [418. 屏幕可显示句子的数量](solution/400-499/0418.sentence-screen-fitting/)