Two methods: 1. Traverse 2. Divide & Conquer // Traverse: usually do not have return value public class Solution { public void traverse(TreeNode root) { if (root == null) return; traverse(root.left); traverse(root.right); } } // Divide & Conquer:…

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 singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. Hide Tags Depth-first Search Linked List       这题是将链表变成二叉树,比较麻烦的遍历过程,因为链表的限制,所以深度搜索的顺序恰巧是链表的顺序,通过设置好递归函数的参数,可以在深度搜索时候便可以遍历了.   TreeNode * he…

Given an array where elements are sorted in ascending order, convert it to a height balanced BST. 解题思路: 1. 找到数组的中间节点将其置为根节点 2. 左边的即为左子树 3. 右边的即为右子树 4. 递归求解 /** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * Tr…

题意 略 分析 1.首先要了解到BST的中序遍历是递增序列 2.我们用一个临时节点tmp储存p的中序遍历的下一个节点,如果p->right不存在,那么tmp就是从root到p的路径中大于p->val的最小数,否则就遍历p的右子树,找到最左边的节点即可 代码 class Solution { public: /* * @param root: The root of the BST. * @param p: You need find the successor node of p. * @re…

Use one queue + size variable public class Solution { public ArrayList<ArrayList<Integer>> levelOrder(TreeNode root) { ArrayList result = new ArrayList(); if (root == null) return result; Queue<TreeNode> queue = new LinkedList<TreeNod…

Validate Binary Search Tree Total Accepted: 23828 Total Submissions: 91943My Submissions 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…

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…

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?   法I:BST的中序遍历结果是递增序列.把这个递增序列…

二叉树(Binary Tree)是最简单的树形数据结构,然而却十分精妙.其衍生出各种算法,以致于占据了数据结构的半壁江山.STL中大名顶顶的关联容器--集合(set).映射(map)便是使用二叉树实现.由于篇幅有限,此处仅作一般介绍(如果想要完全了解二叉树以及其衍生出的各种算法,恐怕要写8~10篇). 1)二叉树(Binary Tree) 顾名思义,就是一个节点分出两个节点,称其为左右子节点:每个子节点又可以分出两个子节点,这样递归分叉,其形状很像一颗倒着的树.二叉树限制了每个节点最多有两个子节…