摘要：
Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST. According to the definition of LCA on Wikipedia 阅读全文
摘要：
由于BST的性质，所以右子树或者左子树中Node的值是连续的： 左子树 = [1, i -1], root = i, 右子树 = [i + 1, n]。使用一个递归函数构造这个BST。其中返回值应该是所有的Unique BST的root node。 阅读全文
摘要：
Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST' 阅读全文
摘要：
Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only 阅读全文
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：
根据提示，本题等价于pre order traverse遍历，并且依次把所有的节点都存成right child，并把left child定义成空集。用递归的思想，那么如果分别把左右子树flatten成list，我们有： 1 / \ 2 5 \ \ 3 6 <- rightTail \ 4 <- le 阅读全文
摘要：
There are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every 阅读全文