作者: 负雪明烛 id: fuxuemingzhu 个人博客:http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 递归 日期 题目地址:https://leetcode.com/problems/diameter-of-binary-tree/#/description 题目描述 Given a binary tree, you need to compute the length of the diameter of the tree. The diameter…

题目如下: 解题思路:最长的周长一定是树中某一个节点(不一定是根节点)的左右子树中的两个叶子节点之间的距离,所以最简单的办法就是把树中所有节点的左右子树中最大的两个叶子节点之间的距离求出来,最终得到最大值. 代码如下: # Definition for a binary tree node. class TreeNode(object): def __init__(self, x): self.val = x self.left = None self.right = None class So…

problem 543. Diameter of Binary Tree 题意: 转换一种角度来看,是不是其实就是根结点1的左右两个子树的深度之和呢.那么我们只要对每一个结点求出其左右子树深度之和,这个值作为一个候选值,然后再对左右子结点分别调用求直径对递归函数,这三个值相互比较,取最大的值更新结果res,因为直径不一定会经过根结点,所以才要对左右子结点再分别算一次.为了减少重复计算,我们用哈希表建立每个结点和其深度之间的映射,这样某个结点的深度之前计算过了,就不用再次计算了. solution…

[LeetCode]Minimum Depth of Binary Tree 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. 递归和非递归,此提比较简单.广度优先遍历即可.关键之处就在于如何保持访问深度. 下面是4种代码: im…

题目: Given inorder and postorder traversal of a tree, construct the binary tree. Note:You may assume that duplicates do not exist in the tree. 提示: 题目要求通过一颗二叉树的中序遍历及后续遍历的结果,将这颗二叉树构建出来,另外还有一个已知条件,所有节点的值都是不同的. 首先需要了解一下二叉树不同遍历方式的定义: 前序遍历:首先访问根结点,然后遍历左子树,最…

这道题是LeetCode里的第104道题. 给出题目: 给定一个二叉树,找出其最大深度. 二叉树的深度为根节点到最远叶子节点的最长路径上的节点数. 说明: 叶子节点是指没有子节点的节点. 示例: 给定二叉树 [3,9,20,null,null,15,7], 3 / \ 9 20 / \ 15 7 返回它的最大深度 3 . DFS 递归算法,简单的二叉树题.如果看不懂代码,建议学习一下二叉树,这可是基础啊! 给出代码: 递归法: /** * Definition for a binary tree…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 DFS BFS 日期 题目地址:https://leetcode.com/problems/cousins-in-binary-tree/ 题目描述 In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1. Tw…

题目简述: 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. 解题思路: # Definition for a binary tree node # class TreeNode: # def __init__(self, x):…

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. 简单题,不过注意叶子结点是两个子树都是NULL的指针.只有一个子树NULL的不是. struct TreeNode { int val; TreeNode *left; TreeN…

Description: Given arrays recording 'Preorder and Inorder' Traversal (Problem 105) or  'Inorder and Postorder' (Problem 106), u need build the binary tree. Input: 105. Preorder & Inorder traversal 106. Inorder & Postorder traversal output: A binar…