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 BFS DFS Date 题目地址:https://leetcode.com/problems/find-bottom-left-tree-value/#/description 题目描述 Given a binary tree, find the leftmost value in the last row of the tree. Example…

原题 Given a binary tree, find the leftmost value in the last row of the tree. Example 1: Input: 2 / 1 3 Output: 1 Example 2: Input: 1 / \ 2 3 / / \ 4 5 6 / 7 Output: 7 Note: You may assume the tree (i.e., the given root node) is not NULL. 解析 查找最后一层最左侧…

[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…

[LeetCode]99. Recover Binary Search Tree 解题报告(Python) 标签(空格分隔): LeetCode 题目地址:https://leetcode.com/problems/recover-binary-search-tree/description/ 题目描述: Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without chan…

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. 来源:力扣(LeetCode)链接:https://leetcode-cn.com/problems/recover-binary-search-tree著作权归领扣网络所有.商业转载请联系官方授权,非商业转载请注明出处. [题意分析] 对于一个BST应该了解的一个重…

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 递归 日期 题目地址:https://leetcode.com/problems/construct-binary-search-tree-from-preorder-traversal/ 题目描述 Return the root node of a binary search tree that matches the given preorder…

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…

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 BST的中序遍历是有序的 日期 题目地址:https://leetcode.com/problems/validate-binary-search-tree/#/description 题目描述 Given a binary tree, determine if it is a valid binary search tree (BST). A…

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…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 公众号:负雪明烛 本文关键词:Leetcode, 力扣,Trie, 前缀树,字典树,208,Python, C++, Java 目录 题目描述 题目大意 解题方法 从二叉树说起 前缀树 构建 查询 应用 代码 刷题心得 日期 题目地址:https://leetcode.com/problems/implement-trie-prefix-tree/description/ 题目描述 I…

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 重建二叉树 数组保存节点 中序遍历时修改指针 参考资料 日期 题目地址:https://leetcode.com/problems/increasing-order-search-tree/description/ 题目描述 Given a tree, rearrange the tree in in-order so that the leftmo…

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…

题目: Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node contains only nodes with…

Implement Trie (Prefix Tree) Implement a trie with insert, search, and startsWith methods. Note:You may assume that all inputs are consist of lowercase letters a-z. 一个字母代表一个子树,因此为26叉树,end标记表示是否存在以该字母为结尾的字符串. class TrieNode { public: TrieNode* childre…

Validate Binary Search Tree Given a binary tree, determine if it is a valid binary search tree (BST). Assume a BST is defined as follows: The left subtree of a node contains only nodes with keys less than the node's key. The right subtree of a node c…

Recover Binary Search Tree Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Note:A solution using O(n) space is pretty straight forward. Could you devise a constant space solution? 基本…

http://oj.leetcode.com/problems/maximum-depth-of-binary-tree/ public class Solution { public int maxDepth(TreeNode root) { if(root!=null){ int depth=0; InOrder(root,depth); } return max; } public int max=0; private void InOrder(TreeNode root, int dep…

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…

题目如下: Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a node in s and all of this node's descendants. The tree s could also be con…

题目如下: Return the root node of a binary search tree that matches the given preorder traversal. (Recall that a binary search tree is a binary tree where for every node, any descendant of node.left has a value < node.val, and any descendant of node.righ…

题目如下: 解题思路:我的方法是先用递归的方法找出最左边的节点,接下来再对树做一次递归中序遍历,找到最左边节点后将其设为root,其余节点依次插入即可. 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 Solution(object): n…

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…

题目如下: In a binary tree, the root node is at depth 0, and children of each depth k node are at depth k+1. Two nodes of a binary tree are cousins if they have the same depth, but have different parents. We are given the root of a binary tree with uniqu…

A trie (pronounced as "try") or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various applications of this data structure, such as autocomplete and spellchecker. Implement the…

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-cn.com/problems/convert-binary-search-tree-to-sorted-doubly-linked-list/ 题目描述 Convert a BST to a sorted circular doubly-linked list in-place. Thin…

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 动态规划 日期 题目地址:https://leetcode-cn.com/problems/paint-fence/ 题目描述 There is a fence with n posts, each post can be painted with one of the k colors. You have to paint all the posts…

[LeetCode]199. Binary Tree Right Side View 解题报告(Python) 标签: LeetCode 题目地址:https://leetcode.com/problems/binary-tree-right-side-view/description/ 题目描述: Given a binary tree, imagine yourself standing on the right side of it, return the values of the no…