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ProblemGiven a binary search tree, write a function kthSmallest to find the kth smallest element in it.Note: You may assume k is always valid, 1 ≤ k ≤ BST's total elements.Follow up:What if the BST i

ProblemGiven 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 be

相似题目： 二叉树的前序遍历：http://blog.youkuaiyun.com/arcome/article/details/53672748 二叉树的中序遍历： 二叉树的后序遍历：ProblemGiven a binary tree, return the preorder traversal of its nodes' values.Note: Recursive solution

相似题目： 二叉树的前序遍历：http://blog.youkuaiyun.com/Arcome/article/details/53672912 二叉树的中序遍历：http://blog.youkuaiyun.com/arcome/article/details/53672748 二叉树的后序遍历：ProblemGiven a binary tree, return the postorder trav

ProblemGiven a binary tree, return the inorder traversal of its nodes' values.Note: Recursive solution is trivial, could you do it iteratively?ExampleGiven binary tree [1,null,2,3], 1 \ 2

ProblemFind the sum of all left leaves in a given binary tree.Example 3 / \ 9 20 / \ 15 7There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

ProblemInvert a binary tree.Example 4 / \ 2 7 / \ / \1 3 6 9-> 4 / \ 7 2 / \ / \9 6 3 1Algorithm整理一下题意：翻转一棵二叉树。首先想到的当然是递归解法。对每个节点，都翻转左右子树。代码如下。//递归版本，用时0

ProblemGiven a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).Example this binary tree [1,2,2,3,4,4,3] is symmetric: 1 / \ 2 2 / \ / \3 4 4 3But t

ProblemGiven an encoded string, return it's decoded string.The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. Note that k is

ProblemGiven an array where elements are sorted in ascending order, convert it to a height balanced BST.ExampleInput:[1,2,3]Output: 1 /\ 2 3Algorithm整理一下题意：给定一个升序数组，要求将其转化为一课平衡二叉树经典的树类型题目。采

ProblemThe thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After

ProblemGiven two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value.ExampleDete

ProblemGiven a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.Subscribe to see which companies ask

ProblemGiven 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 dif

ProblemImplement 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()

ProblemYou are given a binary tree in which each node contains an integer value.Find the number of paths that sum to a given value.The path does not need to start or end at the root or a leaf, but it m

Problem给定两棵二叉树，判断这两棵二叉树是否相等。当且仅当两棵树结构相同且对应节点的取值也相同时，两棵二叉树相等。ExampleA: 1 / \ 2 3 / \ \5 6 7B: 1 / \ 2 3 / \ / 5 6 7 C: 1 / \ 2 3 / \ \5 6 7A==C,A!=BAlgorith