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Balanced Binary TreeGiven 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 subt

Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next leve

Convert Sorted Array to Binary Search TreeGiven an array where elements are sorted in ascending order, convert it to a height balanced BST.Using binary search to solve th

Binary Tree Upside DownGiven a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down a

Count Complete Tree NodesGiven a complete binary tree, count the number of nodes.Definition of a complete binary tree from Wikipedia:In a complete binary tree every level, except possibly

Validate Binary Search Tree

Binary Tree Maximum Path Sum Given a binary tree, find the maximum path sum.The path may start and end at any node in the tree.For example:Given the below binary tree, 1

Binary Tree Right Side ViewGiven a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.For example:Given t

Populating Next Right Pointers in Each NodeGiven a binary tree struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }P

Kth Smallest Element in a BSTGiven 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 e

Recover Binary Search TreeTwo elements of a binary search tree (BST) are swapped by mistake.Recover the tree without changing its structure.Note:A solution using O(n)

preorder, inorder, postorder traversalGiven a binary tree, return the preorder traversal of its nodes' values.For example:Given binary tree {1,#,2,3}, 1 \ 2 / 3

Flatten Binary Tree to Linked ListGiven a binary tree, flatten it to a linked list in-place.For example,Given 1 / \ 2 5 / \ \ 3 4 6Th

Construct Binary Tree from Inorder and Postorder TraversalGiven inorder and postorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the

Symmetric TreeGiven a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3

Serialize and Deserialize a binary treevoid Serialize(TreeNode node) { if (node == null) { System.out.print("#" + " "); return; } System.out.print(node.val + " "); Serialize(nod

Binary Tree Level Order Traversal IIGiven a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For examp

Maximum depth of binary tree and minimum depth of binary tree.Maximum/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeN

Same TreeGiven 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.

Path SumGiven a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary

Unique Binary Search TreesGiven 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

5

Binary Search Tree IteratorImplement 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 smalle

Sum Root to Leaf NumbersGiven a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.An example is the root-to-leaf path 1->2->3 which repre

Construct Binary Tree from Preorder and Inorder TraversalGiven preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in t

Lowest Common Ancestor of a Binary Search TreeGiven a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to the