题解 + Python/Java/C++/Go 代码：
- Q1 https://leetcode.cn/problems/minimum-element-after-replacement-with-digit-sum/solution/bu-yong-zi-fu-chuan-de-xie-fa-pythonjava-zdsy/
- Q2 https://leetcode.cn/problems/maximize-the-total-height-of-unique-towers/solution/cong-zui-da-yuan-su-kai-shi-tan-xin-pyth-s0t9/
- Q3 https://leetcode.cn/problems/find-the-lexicographically-smallest-valid-sequence/solution/qian-hou-zhui-fen-jie-zi-xu-lie-pi-pei-t-le8d/
- Q4 https://leetcode.cn/problems/find-the-occurrence-of-first-almost-equal-substring/solution/qian-hou-zhui-fen-jie-z-shu-zu-pythonjav-0est/
具体请看 视频讲解，欢迎点赞关注~