LeetCode 347. Top K Frequent Elements

https://leetcode.com/problems/top-k-frequent-elements/description/

hash map + heap

Time complicity: O(N + logk)

 

LeetCode 110. Balanced Binary Tree

https://leetcode.com/problems/balanced-binary-tree/description/

 

LeetCode 128. Longest Consecutive Sequence

https://leetcode.com/problems/longest-consecutive-sequence/description/