题目 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. 分析 判断给定二叉树是否为二叉平衡树,即任一节点的左右子树高度差…

题目: 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. 思路: 题目的大意是[判断一个二叉树是不是平衡二叉树 首先了解…

题目 分析 按要求转换二叉树: 分析转换要求,发现,新的二叉树是按照原二叉树的先序遍历结果构造的单支二叉树(只有右子树). 发现规则,便容易处理了.得到先序遍历,构造即可. AC代码 /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NUL…

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. Show Tags Show Similar Problems 分析 跟上一道题同样的道理. AC代码 class Solution { public: template <typename Iter> TreeN…

题目 Given preorder and inorder traversal of a tree, construct the binary tree. Note: You may assume that duplicates do not exist in the tree. 分析 给定一颗二叉树的前序和中序遍历序列,求该二叉树. 我们手动做过很多这样的题目,掌握了其规则~ 前序遍历第一个元素为树的root节点,然后在中序序列中查找该值,元素左侧为左子树,右侧为右子树: 求出左子树个数cou…

题目 分析 交换二叉树的左右子树. 递归非递归两种方法实现. AC代码 class Solution { public: //递归实现 TreeNode* invertTree(TreeNode* root) { if (!root) return root; TreeNode *tmp = root->left; root->left = invertTree(root->right); root->right = invertTree(tmp); return root; }…

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…

题目描述 (原题目链接) Given a binary tree, return the inorder traversal of its nodes' values. For example:Given binary tree [1,null,2,3], 1 \ 2 / 3 return [1,3,2]. 解题思路 这道题目是关于二叉树中序遍历的迭代实现.之前就总结过二叉树的非递归实现.可是做题的时候太久没刷题,就断路了.所以重新思考了一种解法.主要想法是:用一个标记位标记是否需要遍历当前节点…

题目 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? 分析 给定一颗二叉排序树,它的两个节点被交换,要求…

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 k…