摘要：
Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the dept 阅读全文
摘要：
Given a binary search tree (BST) with duplicates, find all the mode(s) (the most frequently occurred element) in the given BST. Assume a BST is define 阅读全文
摘要：
Given a non-empty string check if it can be constructed by taking a substring of it and appending multiple copies of the substring together. You may a 阅读全文