摘要： 1、问题描述 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 contai 阅读全文

摘要： 1、问题描述 Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following un 阅读全文

摘要： 1、问题描述 Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally iden 阅读全文

摘要： 1、问题描述 Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is 阅读全文

摘要： 1、问题描述 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 t 阅读全文

摘要： 1、问题描述 You need to find the largest value in each row of a binary tree. Example: 2、边界条件:root==null 3、思路：层级遍历，每一层找到最大值，记录 4、代码实现 5、api 阅读全文

摘要： 1、问题描述 Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following un 阅读全文

摘要： 1、二叉树 完全二叉树（complete binary tree）：除了最下面一层都是满的，最下面一层也是优先排列在左边。这样的话父亲节点和孩子节点就在序号上面有关系： 父亲节点为n，那么子节点的编号为2n和2n+1。这样就可以操作序号来操作完全二叉树。 A1 / \ B2 C3 / \ / \ D 阅读全文

摘要： 1、问题描述 Given a binary tree, return all root-to-leaf paths. For example, given the following binary tree: All root-to-leaf paths are: 2、边界条件：root为null； 阅读全文

摘要： 1、问题描述 Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom. 阅读全文