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 keys…

4.5 Implement a function to check if a binary tree is a binary search tree. LeetCode上的原题,请参见我之前的博客Validate Binary Search Tree 验证二叉搜索树.…

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 keys…

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 keys…

给定一个二叉树,判断其是否是一个有效的二叉搜索树.一个二叉搜索树有如下定义:    左子树只包含小于当前节点的数.    右子树只包含大于当前节点的数.    所有子树自身必须也是二叉搜索树.示例 1:    2   / \  1   3二叉树[2,1,3], 返回 true.示例 2:    1   / \  2   3二叉树 [1,2,3], 返回 false.详见:https://leetcode.com/problems/validate-binary-search-tree/descr…

给定一个二叉树,判断其是否是一个有效的二叉搜索树. 假设一个二叉搜索树具有如下特征: 节点的左子树只包含小于当前节点的数. 节点的右子树只包含大于当前节点的数. 所有左子树和右子树自身必须也是二叉搜索树. 示例 1: 输入: 2 / \ 1 3 输出: true 示例 2: 输入: 5 / \ 1 4   / \   3 6 输出: false 解释: 输入为: [5,1,4,null,null,3,6].   根节点的值为 5 ,但是其右子节点值为 4 . class Solution { p…

Given an array of numbers, verify whether it is the correct preorder traversal sequence of a binary search tree. You may assume each number in the sequence is unique. Follow up: Could you do it using only constant space complexity? 这道题让给了我们一个一维数组,让我们…

Given an array of numbers, verify whether it is the correct preorder traversal sequence of a binary search tree. You may assume each number in the sequence is unique. Consider the following binary search tree: 5 / \ 2 6 / \ 1 3 Example 1: Input: [5,2…

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? confused what "{1,#,2,3}"…

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? confused what"{1,#,2,3}&quo…

Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST. Calling next() will return the next smallest number in the BST. Note: next() and hasNext() should run in average O(1) time and uses…

判断二叉搜索树的方法是: 中序遍历形成递增序列 //全局变量记录中序遍历产生的序列,因为要递归,所以要用全局变量 List<Integer> list = new ArrayList<>(); public boolean isValidBST(TreeNode root) { /* 这里要注意二叉搜索树的左子树的每个节点都要小于根节点,不只是左孩子,右子树也同样, 常犯的一个错误就是只是判断了左孩子和右孩子 正确方法是:中序遍历法,中序遍历之后的结果是一个递增序列 判断是否是二叉…

Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST. Calling next() will return the next smallest number in the BST. Note: next() and hasNext() should run in average O(1) time and uses…

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has…

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Example 1: Input: [1,3,null,null,2]   1   /  3   \   2 Output: [3,1,null,null,2]   3   /  1   \   2 Example 2: Input: [3,1,4,null,null…

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. Example 1: Input: [1,3,null,null,2] 1 / 3 \ 2 Output: [3,1,null,null,2] 3 / 1 \ 2 Example 2: Input: [3,1,4,null,null,2] 3 / \ 1 4 / 2…

题目: Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed bi…

构建二叉搜索树 /* 利用二叉搜索树的特点:根节点是中间的数 每次找到中间数,左右子树递归子数组 */ public TreeNode sortedArrayToBST(int[] nums) { return builder(nums,0,nums.length-1); } public TreeNode builder(int[] nums,int left,int right) { if (left>right) return null; int mid = (left+right)/2;…

Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 这道题实际上是Catalan Number卡塔兰数的一个例子,如果对卡塔兰数不熟悉的童鞋可能真…

实现一个二叉搜索树迭代器.你将使用二叉搜索树的根节点初始化迭代器.调用 next() 将返回二叉搜索树中的下一个最小的数.注意: next() 和hasNext() 操作的时间复杂度是O(1),并使用 O(h) 内存,其中 h 是树的高度. 详见:https://leetcode.com/problems/binary-search-tree-iterator/description/ Java实现: /** * Definition for a binary tree node. * publ…

Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 题意:给定数n,二叉树的结点的值分别为1,2....n.问能组成多少种不同的二叉搜索树. 二叉…

［抄题］: Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed…

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 keys…

博主欢迎转载,但请给出本文链接,我尊重你,你尊重我,谢谢~http://www.cnblogs.com/chenxiwenruo/p/6789220.html特别不喜欢那些随便转载别人的原创文章又不给出链接的所以不准偷偷复制博主的博客噢~~ 题意:给出一个序列,问你是否是一棵二叉搜索树或者是其镜像的前序遍历.并且输出其后序遍历. 一开始没考虑到只有一个子树...比如BST78 11 9 8 10 13 12MIRROR78 11 13 12 9 10 8所以要先判断是否为BST,不是的话再判断是…

实现一个二叉搜索树迭代器.你将使用二叉搜索树的根节点初始化迭代器. 调用 next() 将返回二叉搜索树中的下一个最小的数. 注意: next() 和hasNext() 操作的时间复杂度是O(1),并使用 O(h) 内存,其中 h 是树的高度. 二叉树的中序遍历 class BSTIterator { public: stack<TreeNode*> s; TreeNode *cur; BSTIterator(TreeNode *root) { cur = root; while(cur) {…

二叉排序树中有两个节点被交换了,要求把树恢复成二叉排序树. 详见:https://leetcode.com/problems/recover-binary-search-tree/submissions/ Java实现: /** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val =…

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 co…

Medium! 题目描述: 给定一个二叉树,判断其是否是一个有效的二叉搜索树. 一个二叉搜索树具有如下特征: 节点的左子树只包含小于当前节点的数. 节点的右子树只包含大于当前节点的数. 所有左子树和右子树自身必须也是二叉搜索树. 示例 1: 输入: 2 / \ 1 3 输出: true 示例 2: 输入: 5 / \ 1 4   / \   3 6 输出: false 解释: 输入为: [5,1,4,null,null,3,6].   根节点的值为 5 ,但是其右子节点值为 4 . 解题思路:…

Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target. Note: Given target value is a floating point. You are guaranteed to have only one unique value in the BST that is closest to the target.…

Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 此题是卡塔兰数的一个应用.注意是BST而不是普通的Binary Tree,所以要满足左比根小,…