Update changes

Author: CompetitiveLin

README.md

@@ -26,6 +26,8 @@
 
 | 最近提交时间 | 题目 | 题目难度 | 提交次数| 重刷次数 |
 | ---- | ---- | ---- | ---- | ---- |
+| 2023-12-28 17:12 | [#279 完全平方数](https://leetcode.cn/problems/perfect-squares) | MEDIUM | 2 | 1 |
+| 2023-12-28 13:30 | [#5 最长回文子串](https://leetcode.cn/problems/longest-palindromic-substring) | MEDIUM | 2 | 1 |
 | 2023-12-26 22:24 | [#1143 最长公共子序列](https://leetcode.cn/problems/longest-common-subsequence) | MEDIUM | 2 | 1 |
 | 2023-12-24 12:30 | [#567 字符串的排列](https://leetcode.cn/problems/permutation-in-string) | MEDIUM | 3 | 1 |
 | 2023-12-23 10:30 | [#1962 移除石子使总数最小](https://leetcode.cn/problems/remove-stones-to-minimize-the-total) | MEDIUM | 1 | 1 |