https://leetcode.com/problems/continuous-subarrays/description/

Count subarrays with difference <= 2 #medium #monotonic_queue #tree_set

https://leetcode.com/problems/reverse-odd-levels-of-binary-tree/description/

Odd-levels reversal in a perfect tree #medium #dfs #bfs #tree

https://leetcode.com/problems/find-the-maximum-sum-of-node-values/description/

Max sum by k-xoring edges #hard #tree #dp