A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. 太简单了,签到题.…

problem 965. Univalued Binary Tree 参考 1. Leetcode_easy_965. Univalued Binary Tree; 完…

题目来源: https://leetcode.com/problems/univalued-binary-tree/submissions/ 自我感觉难度/真实难度: 题意: 分析: 自己的代码: class Solution(object): def isUnivalTree(self, root): """ :type root: TreeNode :rtype: bool """ return self.dsf(root.val,root)…

A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. Example 1: Input: [1,1,1,1,1,null,1] Output: true Example 2: Input: [2,2,2,5,2] Output: false Note: The number of nodes i…

题目要求 A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. 题目分析及思路 题目要求当输入的二叉树的每个结点都有相同的值则返回true,否则返回false.可以使用队列保存每个节点,用val保存root节点的值.如果弹出的数字不等于val不等于root节点就立刻返回false.如果全部判断完…

题目如下: A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. Example 1: Input: [1,1,1,1,1,null,1] Output: true Example 2: Input: [2,2,2,5,2] Output: false Note: The number of 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 BFS DFS 日期 题目地址:https://leetcode.com/problems/univalued-binary-tree/ 题目描述 A binary tree is univalued if every node in the tree has the same value. Return true if and only if th…

A binary tree is univalued if every node in the tree has the same value. Return true if and only if the given tree is univalued. Example 1: Input: [1,1,1,1,1,null,1] Output: true Example 2: Input: [2,2,2,5,2] Output: false Note: The number of nodes i…

Given a binary tree with N nodes, each node has a different value from {1, ..., N}. A node in this binary tree can be flipped by swapping the left child and the right child of that node. Consider the sequence of N values reported by a preorder traver…

Print a binary tree in an m*n 2D string array following these rules: The row number m should be equal to the height of the given binary tree. The column number n should always be an odd number. The root node's value (in string format) should be put i…

Return any binary tree that matches the given preorder and postorder traversals. Values in the traversals pre and post are distinct positive integers. Example 1: Input: pre = [1,2,4,5,3,6,7], post = [4,5,2,6,7,3,1] Output: [1,2,3,4,5,6,7] Note: 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. For example, given inorder = [9,3,15,20,7] postorder = [9,15,7,20,3] Return the following binary tree: 3 / \ 9 2…

Given preorder and inorder traversal of a tree, construct the binary tree. Note:You may assume that duplicates do not exist in the tree. For example, given preorder = [3,9,20,15,7] inorder = [9,3,15,20,7] Return the following binary tree: 3 / \ 9 20…

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. Example 1: Given the following tre…

Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: 1 / \ 2 5 / \ \ 3 4 6 The flattened tree should look like: 1 \ 2 \ 3 \ 4 \ 5 \ 6 Solution 1: # Definition for a binary tree node. # class TreeNode(objec…

Invert a binary tree. Example: Input: 4 / \ 2 7 / \ / \ 1 3 6 9 Output: 4 / \ 7 2 / \ / \ 9 6 3 1 /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ c…

这是悦乐书的第366次更新,第394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228题(顺位题号是965).如果树中的每个节点具有相同的值,则二叉树是单一的.当且仅当给定树是单一时才返回true. 1 / \ 1 1 / \ \ 1 1 1 输入: [1,1,1,1,1,null,1] 输出: true 2 / \ 2 2 / \ 5 2 输入: [2,2,2,5,2] 输出: false 注意: 给定树中的节点数量将在[1,100]范围内. 每个节点的值将是…

1.题目描述 2.问题分析 遍历一遍树,然后将所有节点的数值放入到一个set中,最后检查set中元素的个数是否为1. 3.代码 bool isUnivalTree(TreeNode* root) { set<int> s; preOrder(root, s); ; } void preOrder(TreeNode* root, set<int> &s) { if (root == NULL) return; s.insert(root->val); preOrder(…

如果二叉树每个节点都具有相同的值,那么该二叉树就是单值二叉树. 只有给定的树是单值二叉树时,才返回 true:否则返回 false. 示例 1: 输入:[1,1,1,1,1,null,1] 输出:true 示例 2: 输入:[2,2,2,5,2] 输出:false 提示: 给定树的节点数范围是 [1, 100]. 每个节点的值都是整数,范围为 [0, 99] . class Solution { public: int val = -1; bool isUnivalTree(TreeNode*…

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 题目 Invert a binary tree. 4 / \ 2 7 / \ / \ 1 3 6 9 to 4 / \ 7 2 / \ / \ 9 6 3 1 接口: public TreeNode invertTree(TreeNode root) 2 思路 反转一颗二叉树. 可以用递归和非递归两种方法来解. 递归的方法,写法非常简洁,五行代码搞定,交换当前左右节点,并直接调用递归即可. 非递归的方法,参考树的层序遍历,借助Queue来辅助,先把根节点排入队列中,然后从队中取出来,交换其左…

Given a binary tree, we install cameras on the nodes of the tree. Each camera at a node can monitor its parent, itself, and its immediate children. Calculate the minimum number of cameras needed to monitor all nodes of the tree. Example 1: Input: [0,…

问题: Serialize and Deserialize Binary Tree 描述: 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 rec…

题目描述 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…

题目描述 144. Binary Tree Preorder Traversal 94. Binary Tree Inorder Traversal 145. Binary Tree Postorder Traversal 前序排列 :根-左-右 中序排列: 左-根-右 后序排列:左-右-根 参考答案 // PreOrder /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *le…

Given a binary tree, return the vertical order traversal of its nodes values. For each node at position (X, Y), its left and right children respectively will be at positions (X-1, Y-1) and (X+1, Y-1). Running a vertical line from X = -infinity to X =…

问题描述 Given a binary tree, return the inorder traversal of its nodes' values. (左 - 根 - 右) Example: Input: [1,null,2,3] 1 \ 2 / 3 Output: [1,3,2] Follow up: Recursive solution is trivial, could you do it iteratively? 参考答案 /** * Definition for a binary…

Given the root of a binary tree with N nodes, each node in the tree has node.val coins, and there are N coins total. In one move, we may choose two adjacent nodes and move one coin from one node to another.  (The move may be from parent to child, or…

Given a binary tree, write a function to get the maximum width of the given tree. The width of a tree is the maximum width among all levels. The binary tree has the same structure as a full binary tree, but some nodes are null. The width of one level…

Design an algorithm to encode an N-ary tree into a binary tree and decode the binary tree to get the original N-ary tree. An N-ary tree is a rooted tree in which each node has no more than N children. Similarly, a binary tree is a rooted tree in whic…