摘要：
In a binary tree, a lonely node is a node that is the only child of its parent node. The root of the tree is not lonely because it does not have a par 阅读全文
摘要：
A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. Example 1: Input: [1, 阅读全文
摘要：
Given the root node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [ 阅读全文