二叉平衡树好火啊.差点儿每一个公司的笔试题里都有它.考了好多次我都不会,挂笔试非常有可能就是由于它.另一个它的同伙叫二叉搜索树,貌似人气比它还要高一些. 二叉平衡树是什么样的树呢.是每一个节点的左右子树高度相差绝对值都不超过1.好.你说你最终回了,这不非常easy吗,求一下根节点的左右字数高度,假设满足,他就是.否则就不是嘛.不是啊亲,要求是全部节点都满足这个条件,推断的时候必须每一个节点都验证的! 扯了这么长.事实上看看代码就明确了,怎么有种在贴吧发言要凑够15字的感觉. int getHei…

构造方式跟中序与后序全然一样,并且一般都习惯正着来,所以更简单. 代码是之前写的,没实用库函数,不应该. TreeNode *buildIt(vector<int> &preorder, int start1, vector<int> &inorder, int start2, int len){ if(len <= 0) return NULL; TreeNode *root = new TreeNode(preorder[start1]); int i =…

这道题是为数不多的感觉在读本科的时候见过的问题. 人工构造的过程是如何呢.兴许遍历最后一个节点一定是整棵树的根节点.从中序遍历中查找到这个元素,就能够把树分为两颗子树,这个元素左側的递归构造左子树,右側的递归构造右子树.元素本身分配空间,作为根节点. 于set和map容器不同的是.vector容器不含find的成员函数.应该用stl的库函数,好在返回的也是迭代器,而vector的迭代器之间是能够做减法的.偏移量非常方便的得到. TreeNode *buildRec(vector<int> &a…

有了上面的教训,这道题就简单多了,什么时候该更新pre是明白的了,倒是有个细节,二叉搜索树中是不同意有相等节点的,所以题目的要求用黑体字标明了.写的时候注意就能够了. class Solution { public: TreeNode *pre = NULL; bool isValidBST(TreeNode *root) { if(root == NULL) return true; bool res = true; if(root->left) res &= isValidBST(roo…

这道题事实上跟二叉搜索树没有什么关系,给定n个节点,让你求有多少棵二叉树也是全然一样的做法.思想是什么呢,给定一个节点数x.求f(x),f(x)跟什么有关系呢,当然是跟他的左右子树都有关系.所以能够利用其左右子树的结论.大问题被成功转化成了小问题.最熟悉的方法是递归和dp.这里显然有大量的反复计算.用dp打表好一些. 后来实验的同学说,这事实上是一个Catalan数,上网查了一下,果然啊.Catalan数是这样子的: h(0) = 1, h(1) = 1; 递推式:h(n)= h(0)*h(n-…

二进制相加,本质上就是大整数加法,有关大整数加法我的舍友教过我一个非常好的方法,先用一个int数组保存结果,将两个数相应位置相加,所有加完后.再统一处理进位的问题.这种方法相同适用于大整数的乘法. 这个题没什么特别的,注意一下进位别搞错了即可了,还有事实上不用像我写的这么麻烦,能够一開始先推断哪个更长一些.交换一下.代码会简洁非常多. class Solution { public: string addBinary(string a, string b) { int l1 = a.length…

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…

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. 算法1:dfs递归的求解 class Solution { public: int minDepth(T…

Description: 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 a…

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…

Serialize and Deserialize Binary Tree 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 reconstruct…

一天一道LeetCode 本系列文章已全部上传至我的github,地址:ZeeCoder's Github 欢迎大家关注我的新浪微博,我的新浪微博 欢迎转载,转载请注明出处 (一)题目 来源:https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/ Given inorder and postorder traversal of a tree, construct the b…

LeetCode--Maximum Depth of Binary Tree Question 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. Answer /** * Definition for a binary tree…

题目 Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root). For example: Given binary tree {3,9,20,#,#,15,7}, return its bottom-up level order traversal as: 分析 与…

题目如下: We are given the root node of a maximum tree: a tree where every node has a value greater than any other value in its subtree. Just as in the previous problem, the given tree was constructed from an list A (root = Construct(A)) recursively with…

[LeetCode]106. Construct Binary Tree from Inorder and Postorder Traversal 解题报告(Python) 标签: LeetCode 题目地址:https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/description/ 题目描述: Given inorder and postorder traversal…

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…

一天一道LeetCode 本系列文章已全部上传至我的github,地址:ZeeCoder's Github 欢迎大家关注我的新浪微博,我的新浪微博 欢迎转载,转载请注明出处 (一)题目 来源:https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/ Given preorder and inorder traversal of a tree, construct the bin…

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 迭代 日期 题目地址: https://leetcode.com/problems/invert-binary-tree/ 题目描述 Invert a binary tree. Example: Input: 4 / \ 2 7 / \ / \ 1 3 6 9 Output: 4 / \ 7 2 / \ / \ 9 6 3 1 Trivia:…

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/maximum-binary-tree-ii/ 题目描述 We are given the root node of a maximum tree: a tree where every node has a value greater than any other v…

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 前序遍历 日期 题目地址:https://leetcode.com/problems/flip-binary-tree-to-match-preorder-traversal/ 题目描述 Given a binary tree with N nodes, each node has a different value from {1, -, N}.…

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/maximum-binary-tree/description/ 题目描述 Given an integer array with no duplicates. A maximum tree building on this array is defined as fol…

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/construct-binary-tree-from-preorder-and-inorder-traversal/description/ 题目描述 Given preorder and inorder traversal of a tree, construct t…

Given a binary tree, find all leaves and then remove those leaves. Then repeat the previous steps until the tree is empty. Example: Given binary tree 1 / \ 2 3 / \ 4 5 Returns [4, 5, 3], [2], [1]. Explanation: 1. Remove the leaves [4, 5, 3] from the…

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. 求二叉树的最大深度问题用到深度优先搜索DFS,递归的完美应用,跟求二叉树的最小深度问题原理相同.代码如下: C++ 解法一: class Solution { public: in…

------------------------------------- 反转树的基本操作. 可是下面那句话是什么鬼啊,这么牛掰的人都会有这种遭遇,确实抚慰了一点最近面试被拒的忧伤..... AC代码: /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * }…

Given a binary tree, collect a tree's nodes as if you were doing this: Collect and remove all leaves, repeat until the tree is empty. Example: Given binary tree 1 / \ 2 3 / \ 4 5 Returns [4, 5, 3], [2], [1]. Explanation: 1. Removing the leaves [4, 5,…

Problem Link: https://oj.leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/ The basic idea is same to that for Construct Binary Tree from Inorder and Postorder Traversal. We solve it using a recursive function. First, we…

Problem Link: https://oj.leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/ This problem can be easily solved using recursive method. By given the inorder and postorder lists of the tree, i.e. inorder[1..n] and postorde…

Problem Link: http://oj.leetcode.com/problems/balanced-binary-tree/ We use a recursive auxilar function to determine whether a sub-tree is balanced, if the tree is balanced, it also return the depth of the sub-tree. A tree T is balanced if the follow…