判断一棵树是否自对称 可以回忆我们做过的Leetcode 100 Same Tree 二叉树和Leetcode 226 Invert Binary Tree 二叉树 先可以将左子树进行Invert Binary Tree,然后用Same Tree比较左右子树 而我的做法是改下Same Tree的函数,改动的是第27行 /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left;…

判断一棵树是否是平衡树,即左右子树的深度相差不超过1. 我们可以回顾下depth函数其实是Leetcode 104 Maximum Depth of Binary Tree 二叉树 /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL…

4.7 Design an algorithm and write code to find the first common ancestor of two nodes in a binary tree. Avoid storing additional nodes in a data structure. NOTE: This is not necessarily a binary search tree. LeetCode上的原题,请参见我之前的博客Lowest Common Ancest…

[Leetcode] Maximum and Minimum Depth of Binary Tree 二叉树的最小最大深度 (最小有3种解法) 描述 解析 递归深度优先搜索 当求最大深度时,我们只要在左右子树中取较大的就行了. 然而最小深度时,如果左右子树中有一个为空会返回0,这时我们是不能算做有效深度的. 所以分成了三种情况,左子树为空,右子树为空,左右子树都不为空.当然,如果左右子树都为空的话,就会返回1. 广度优先搜索(类似层序遍历的思想) 递归解法本质是深度优先搜索,但因为我们是求最小…

UVA.548 Tree(二叉树 DFS) 题意分析 给出一棵树的中序遍历和后序遍历,从所有叶子节点中找到一个使得其到根节点的权值最小.若有多个,输出叶子节点本身权值小的那个节点. 先递归建树,然后DFS求解. 代码总览 #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <string> #include <sstre…

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. 给一个二叉树,找出它的最小深度.最小深度是从根节点向下到最近的叶节点的最短路径,就是最短路径的节点个数. 解法1:DFS 解法2: BFS Java: DFS, Time Comp…

Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root. Example:Given a binary t…

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another comput…

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w…

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. 二叉树的经典问题之最小深度问题就是就最短路径的节点个数,还是用深度优先搜索DFS来完成,万能的递归啊...请看代码: /** * Definition for binary tre…