链接：https://leetcode.com/tag/binary-search-tree/
【220】Contains Duplicate III
【315】Count of Smaller Numbers After Self
【327】Count of Range Sum
【352】Data Stream as Disjoint Intervals
【493】Reverse Pairs
【530】Minimum Absolute Difference in BST
【683】K Empty Slots
【699】Falling Squares
【715】Range Module
【731】My Calendar II
【732】My Calendar III
【776】Split BST
【783】Minimum Distance Between BST Nodes
【938】Range Sum of BST