110. 平衡二叉树 给定一个二叉树,判断它是否是高度平衡的二叉树. 本题中,一棵高度平衡二叉树定义为: 一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过1. 示例 1: 给定二叉树 [3,9,20,null,null,15,7] 3 / \ 9 20 / \ 15 7 返回 true . 示例 2: 给定二叉树 [1,2,2,3,3,null,null,4,4] 1 / \ 2 2 / \ 3 3 / \ 4 4 返回 false . PS: 模版一共三步,就是递归的三部曲: 找终止条…

110. 平衡二叉树 110. Balanced Binary Tree 题目描述 给定一个二叉树,判断它是否是高度平衡的二叉树. 本题中,一棵高度平衡二叉树定义为: 一个二叉树每个节点的左右两个子树的高度差的绝对值不超过 1. 每日一算法2019/5/18Day 15LeetCode110. Balanced Binary Tree 示例 1: 给定二叉树 [3,9,20,null,null,15,7] 3 / \ 9 20 / \ 15 7 返回 true. 示例 2: 给定二叉树 [1,2…

给定一个二叉树,判断它是否是高度平衡的二叉树. 本题中,一棵高度平衡二叉树定义为: 一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过1. 示例 1: 给定二叉树 [3,9,20,null,null,15,7] 3 / \ 9 20 / \ 15 7 返回 true . 示例 2: 给定二叉树 [1,2,2,3,3,null,null,4,4] 1 / \ 2 2 / \ 3 3 / \ 4 4 返回 false . #include <iostream> #include <nu…

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. 解题思路: 递归即可,JAVA实现如下: public boolean…

问题 给出一棵二叉树,判断它是否在高度上是平衡的. 对于本问题,高度上平衡的二叉树定义为:每个节点的两棵子树的深度差永远不大于1的一棵二叉树. 初始思路 根据定义,思路应该比较直接:递归计算每个节点左右子树的深度,只要发现一次深度差大于1的情况,即可终止递归返回不平衡的结果.最终代码如下: class Solution { public: bool isBalanced(TreeNode *root) { if(!root) { return true; } isBalanced_ = true…

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public int height(TreeNode root){ if(root == null) return 0; int left_height = hei…

Given an array where elements are sorted in ascending order, convert it to a height balanced BST. 解题思路: 首先要理解,什么叫做height balanced BST Java for LeetCode 110 Balanced Binary Tree,然后就十分容易了,JAVA实现如下: public TreeNode sortedArrayToBST(int[] nums) { return…

LeetCode:平衡二叉树[110] 题目描述 给定一个二叉树,判断它是否是高度平衡的二叉树. 本题中,一棵高度平衡二叉树定义为: 一个二叉树每个节点 的左右两个子树的高度差的绝对值不超过1. 示例 1: 给定二叉树 [3,9,20,null,null,15,7] 3 / \ 9 20 / \ 15 7 返回 true . 示例 2: 给定二叉树 [1,2,2,3,3,null,null,4,4] 1 / \ 2 2 / \ 3 3 / \ 4 4 返回 false . 题目分析 解法的整体过…

剑指offer 面试题39:判断平衡二叉树 提交网址:  http://www.nowcoder.com/practice/8b3b95850edb4115918ecebdf1b4d222?tpId=13&tqId=11192 时间限制:1秒       空间限制:32768K      参与人数:2481 题目描述 输入一棵二叉树,判断该二叉树是否是平衡二叉树. 分析: 平衡二叉树定义 递归解法 AC代码: #include<iostream> #include<vector&…

Leetcode:110. 平衡二叉树 Leetcode:110. 平衡二叉树 点链接就能看到原题啦~ 关于AVL的判断函数写法,请跳转:平衡二叉树的判断 废话不说直接上代码吧~主要的解析的都在上面的链接里了 自顶向下写法 /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), l…

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers. Ensure that numbers within the set are sorted in ascending order. Example 1…

Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. For example: Given "aacecaaa", return "aaacecaaa&qu…

Given a 2D board and a list of words from the dictionary, find all words in the board. Each word must be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same le…

Design a data structure that supports the following two operations: void addWord(word)bool search(word) search(word) can search a literal word or a regular expression string containing only letters a-z or .. A . means it can represent any one letter.…

There are a total of n courses you have to take, labeled from 0 to n - 1. Some courses may have prerequisites, for example to take course 0 you have to first take course 1, which is expressed as a pair: [0,1] Given the total number of courses and a l…

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by…

Say you have an array for which the ith element is the price of a given stock on day i. Design an algorithm to find the maximum profit. You may complete at most k transactions. 解题思路: https://leetcode.com/discuss/18330/is-it-best-solution-with-o-n-o-1…

Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). Find the minimum element. The array may contain duplicates. 解题思路: 参考Java for LeetCode 081 Search in Rotated Sorted Array II J…

Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). Find the minimum element. You may assume no duplicate exists in the array. 解题思路: 本题和Java for LeetCode 033 Search in Rotated S…

The set [1,2,3,…,n] contains a total of n! unique permutations. By listing and labeling all of the permutations in order, We get the following sequence (ie, for n = 3): "123" "132" "213" "231" "312" "…

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example, Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ]] 解题思路: 参考Java for LeetCode 054 Spiral Matrix,修改下…

Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge…

Given an array of non-negative integers, you are initially positioned at the first index of the array. Each element in the array represents your maximum jump length at that position. Determine if you are able to reach the last index. For example: A =…

Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique permutations: [1,1,2], [1,2,1], and [2,1,1]. 解题思路一: 发现Java for LeetCode 046 Permutations自己想多了,代码直接拿来用…

Implement wildcard pattern matching with support for '?' and '*'. '?' Matches any single character. '*' Matches any sequence of characters (including the empty sequence). The matching should cover the entire input string (not partial). The function p…

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example is &…

Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity. 解题思路一: 之前我们有mergeTwoLists(ListNode l1, ListNode l2)方法,直接调用的话,需要k-1次调用,每次调用都需要产生一个ListNode[],空间开销很大.如果采用分治的思想,对相邻的两个ListNode进行mergeTwoLists,每次将规模减少一半,直到…

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null. Return a deep copy of the list. 解题思路: 我们在Java for LeetCode 133 Clone Graph题中做过图的复制,本题和图的复制十分类似,JAVA实现如下: public Random…

Given an unsorted array of integers, find the length of the longest consecutive elements sequence. For example, Given [100, 4, 200, 1, 3, 2], The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4. Your algorithm should run i…

Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that: Only one letter can be changed at a time    Each intermediate word must exist in the dictionary For example, Given:start = "…