Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. Note: A leaf is a node with no children. Example: Given the below binary tree and sum = 22, 5 / \ 4 8…
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 symmetric: 1 / \ 2 2 / \ / \ 3 4 4 3 But the following [1,2,2,null,3,null,3] is not: 1 / \ 2 2 \ \ 3 3 Not…
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 identical and the nodes have the same value. 两颗二叉树完全相同,也就是某个节点的左右孩子,和另外一棵树的的对应节点的左右孩子相等.和镜像对称树那题类似. 代码: class S…
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 depth of the two subtrees of every node never differ by more than 1. 判断一棵树是否为平衡二叉树. 思路:典型的递归,从第一个根节点开始,看…
Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. 代码: /** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * Tr…
Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ \ 7 2 1 return true…
Maximum Depth of Binary Tree Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. 求二叉树的高度,即从根节点到叶节点上所有节点的数量. 解题思路: 这题是难度系数1,频率1的题目……用到的知识点是二叉树D…
上篇中学习了二叉树的DFS深度优先搜索算法,这次学习另外一种二叉树的搜索算法:BFS,下面看一下它的概念: 有些抽象是不?下面看下整个的遍历过程的动画演示就晓得是咋回事啦: 了解其概念之后,下面看下如何实现它?在正式实现逐层遍历之前,需要解决一个问题,那就是:得知道该树有多少层,也就是树的深度如何计算,下面来解决这个问题: 还是基于上篇的搜索二叉树的代码进行实现: public class BinarySearchTree { TreeNode root = null; class TreeNo…
Given two binary trees, write a function to check if they are the same or not. Two binary trees are considered the same if they are structurally identical and the nodes have the same value. Example 1: Input: 1 1 / \ / \ 2 3 2 3 [1,2,3], [1,2,3] Outpu…
Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. Note: A leaf is a node with no children. Example: Given binary tree [3,9,20,null,null,15,7…
Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. Note: A leaf is a node with no children. Example: Given binary tree [3,9,20,null,null,15,7…
