Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. 题意: 一颗二叉搜索树中有2个结点的元素被误换了,要求恢复二叉搜索树的原状. 思路: 中序遍历BST,若发现一次逆序,说明是两个相连结点的误换,直接交换结点的值:若发现两次逆序,则为不相连的两个结点误换,交换错误的结点即可.用一个变量保存先前结点的状态,若发生逆序则记…

Recover Binary Search Tree Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. 互换二叉搜索树中两个位置错误的节点. 思路: 预设三个指针pre,p1,p2.p1用来指向第一个出错的节点,p2用来指向第二个出错的节点. 出错情况有两种,即p1和p2相邻,p1和p2不相邻. 中序遍历此二叉树,用…

Problem Link: https://oj.leetcode.com/problems/recover-binary-search-tree/ We know that the inorder traversal of a binary search tree should be a sorted array. Therefore, we can compare each node with its previous node in the inorder to find the two…

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…

Problem Link: https://oj.leetcode.com/problems/validate-binary-search-tree/ We inorder-traverse the tree, and for each node we check if current_node.val > prev_node.val. The code is as follows. # Definition for a binary tree node # class TreeNode: #…

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? 中序…

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? 题解:需要找到二叉搜索树中乱序的两个节点,并把它们交换回来…

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…

Two elements of a binary search tree (BST) are swapped by mistake. Recover the tree without changing its structure. 首先是O(N)空间的方法,用递归: /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeN…

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}" means? > read more on how binary tree is serialized on OJ. 3…