A binary tree is defined as a tree where each node can have no more than two children. Building a Binary Search Tree: 首先创建一个节点Class public class BtNode { public int Data { get; set; } public BtNode Left { get; set; } public BtNode Right { get; set; }…

先序遍历,用递归来做,简单的不能再简单了.代码如下: (以下仅实现了先序遍历,中序遍历类似,后序遍历和这两个思路不一样,具体详见Binary Tree Postorder Traversal) /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), righ…

Balanced Binary Tree [数据结构和算法]全面剖析树的各类遍历方法 描述 解析 递归分别判断每个节点的左右子树 该题是Easy的原因是该题可以很容易的想到时间复杂度为O(n^2)的方法.即按照定义,判断根节点左右子树的高度是不是相差1,递归判断左右子树是不是平衡的. 根据深度判断左右子树是否平衡 在计算树的高度的同时判断该树是不是平衡的. 即,先判断子树是不是平衡的,若是,则返回子树的高度:若不是,则返回一个非法的数字,如负数. 当一个节点是左右子树有一个不是平衡二叉树则不必继…

二叉树(Binary Tree)是最简单的树形数据结构,然而却十分精妙.其衍生出各种算法,以致于占据了数据结构的半壁江山.STL中大名顶顶的关联容器--集合(set).映射(map)便是使用二叉树实现.由于篇幅有限,此处仅作一般介绍(如果想要完全了解二叉树以及其衍生出的各种算法,恐怕要写8~10篇). 1)二叉树(Binary Tree) 顾名思义,就是一个节点分出两个节点,称其为左右子节点:每个子节点又可以分出两个子节点,这样递归分叉,其形状很像一颗倒着的树.二叉树限制了每个节点最多有两个子节…

前言 第一天的算法都还没有缓过来,直接就进入了第二天的算法学习.前一天一直在整理Binary Search的笔记,也没有提前预习一下,好在Binary Tree算是自己最熟的地方了吧(LeetCode上面Binary Tree的题刷了4遍,目前95%以上能够Bug Free)所以还能跟得上,今天听了一下,觉得学习到最多的,就是把Traverse和Divide Conquer分开来讨论,觉得开启了一片新的天地!今天写这个博客我就尽量把两种方式都写一写吧. Outline: 二叉树的遍历 前序遍历t…

June 8, 2015 我最喜欢的一道算法题目, 二行代码. 编程序需要很强的逻辑思维, 多问几个为什么, 可不可以简化．想一想, 二行代码, 五分钟就可以搞定; 2015年网上大家热议的 Homebrew 的作者 Max Howell 面试 Google 挂掉的一题, 二叉树反转, 七行代码, 相比二行代码, 情有可原! Problem: return the count of binary tree with only one child 想一想, 你要写几行, 六七行, 或小于十行? S…

这是悦乐书的第285次更新,第302篇原创 01 看题和准备 今天介绍的是LeetCode算法题中Easy级别的第153题(顺位题号是671).给定非空的特殊二叉树,其由具有非负值的节点组成,其中该树中的每个节点具有恰好两个或零个子节点. 如果节点具有两个子节点,则该节点的值是其两个子节点中的较小值.给定这样的二叉树,您需要输出由整个树中所有节点的值组成的集合中的第二个最小值.如果不存在这样的第二个最小值,则输出-1.例如: 2 / \ 2 5 / \ 5 7 输出:5 2 / \ 2 2 输出…

这是悦乐书的第277次更新,第293篇原创 01 看题和准备 今天介绍的是LeetCode算法题中Easy级别的第145题(顺位题号是637).给定一个非空二叉树,以数组的形式返回每一层节点值之和的平均值.例如: 3 / \ 9 20 / \ 15 7 输出:[3,14.5,11] 说明:第一层上的节点的平均值为3,第二层上的节点的平均值为14.5,第三层上的节点的平均值为11.因此返回[3,14.5,11]. 注意:节点值的范围在32位有符号整数的范围内. 本次解题使用的开发工具是eclips…

这是悦乐书的第273次更新,第288篇原创 01 看题和准备 今天介绍的是LeetCode算法题中Easy级别的第141题(顺位题号是606).构造一个字符串,该字符串由二叉树中的括号和整数组成,并具有前序遍历方式.null节点需要用空括号对"()"表示. 并且你需要省略所有不影响字符串与原始二叉树之间的一对一映射关系的空括号对.例如: 输入:二叉树:[1,2,3,4] 1 / \ 2 3 / 4 输出:"1(2(4))(3)" 说明:原始字符串需要为"1…

Given inorder and postorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. 这道题之前算法课上好像遇到过,思路也很简单的. 思路:后序序列的最后一个元素就是树根,然后在中序序列中找到这个元素(由于题目保证没有相同的元素,因此可以唯一找到),中序序列中这个元素的左边就是左子树的中序,右边就是右子树的…

[114-Flatten Binary Tree to Linked List(二叉树转单链表)] [LeetCode-面试算法经典-Java实现][全部题目文件夹索引] 原题 Given a binary tree, flatten it to a linked list in-place. For example, Given 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 题目…

[104-Maximum Depth of Binary Tree(二叉树的最大深度)] [LeetCode-面试算法经典-Java实现][全部题目文件夹索引] 原题 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. 题目大意 给…

二叉树基础 满足这样性质的树称为二叉树:空树或节点最多有两个子树,称为左子树.右子树, 左右子树节点同样最多有两个子树. 二叉树是递归定义的,因而常用递归/DFS的思想处理二叉树相关问题,例如LeetCode题目 104. Maximum Depth of Binary Tree: // 104. Maximum Depth of Binary Tree int maxDepth(TreeNode* root) { ; +max(maxDepth(root->left),maxDepth(roo…

1.二叉搜索树:去一个陌生的城市问路到目的地: for each node, all elements in its left subtree are less-or-equal to the node (<=), and all the elements in its right subtree are greater than the node (>). 给予一个已经排序好的整数数组, 生成一个相对合理的二叉搜索树.(?相对合理的?) 给予一个二叉树的根节点,验证该树是否是二叉树搜索树,(…

Balanced Binary Tree Better Solution [LeetCode] https://leetcode.com/submissions/detail/40087813/ Total Accepted: 72203 Total Submissions: 225370 Difficulty: Easy Question Given a binary tree, determine if it is height-balanced. For this problem, a h…

题目如下:https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/ 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 def…

Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array.Example 1:Input: 3 / \ 9 20 / \ 15 7Output: [3, 14.5, 11]Explanation:The average value of nodes on level 0 is 3, on level 1 is 14.5, and on lev…

1 Same Tree https://leetcode.com/problems/same-tree/ 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. 分治的思想,如果root相…

题目: Given a binary tree, find the maximum path sum. For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The path does not need to go through the root. For ex…

Given a binary tree, return the postorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3}, 1 \ 2 / 3 return [3,2,1]. Note: Recursive solution is trivial, could you do it iteratively? 这道题想了很久,后序遍历应该是最麻烦的吧,最容易想到的方法就是直接设置标志位. 相比…

议题:线索二叉树(Threaded Binary Tree) 分析: 为除第一个节点外的每个节点添加一个指向其前驱节点的指针,为除最后一个节点外的每个节点添加一个指向其后续节点的指针,通过这些额外的指针可以某种遍历方式对二叉树进行遍历,而加了这些额外指针的二叉树就是线索二叉树: 对于含有N个节点的二叉树而言,一共有2N个指针,但除了根节点的其他节点都有来自其父节点的指针,所以耗用了N-1个指针,则最终剩下2N-(N- 1)=N+1个空指针:线索二叉树就是利用这些空指针存储具有某种遍历顺序的前驱和…

  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…

题目 The lowest common ancestor (LCA) of two nodes U and V in a tree is the deepest node that has both U and V as descendants. Given any two nodes in a binary tree, you are supposed to find their LCA. Input Specification: Each input file contains one t…

［抄题］: Given a non-empty binary tree, return the average value of the nodes on each level in the form of an array. Example 1: Input: 3 / \ 9 20 / \ 15 7 Output: [3, 14.5, 11] Explanation: The average value of nodes on level 0 is 3, on level 1 is 14.5,…

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. 题意:二叉树中以任意节点为父结点的两棵子树的深度差不超过1,为平衡二叉…

一.题目 Construct Binary Tree from Inorder and Postorder Traversal My Submissions Given inorder and postorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. Show Tags Have you met this ques…

一.题目 Construct Binary Tree from Preorder and Inorder Traversal My Submissions Given preorder and inorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. Show Tags Have you met this questi…

题目链接:Balanced Binary Tree | LeetCode OJ 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 tha…

Sept. 13, 2015 Spent more than a few hours to work on the leetcode problem, and my favorite blogs about this problems: 1. http://siddontang.gitbooks.io/leetcode-solution/content/tree/construct_binary_tree.html 2.http://blog.csdn.net/linhuanmars/artic…

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…