Divide and Conquer

1.Easy

(169)Majority Element

2.Medium

(53)Maximum Subarray

(105)Construct Binary Tree from Preorder and Inorder Traversal

(148)Sort List

(215)Kth Largest Element in an Array

(240)Search a 2D Matrix II

(347)Top K Frequent Elements

3.Hard

(23)Merge k Sorted Lists