Salvatore Labs

LeetCode

LeetCode: 106. Construct Binary Tree from Inorder and Postorder Traversal

The Problem Given two integer arrays inorder and postorder where inorder is the inorder traversal of a binary tree and postorder is the postorder traversal of the same tree, construct and return the binary tree. Example Input: inorder = [9,3,15,20,7], postorder = [9,15,7,20,3] Output:

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LeetCode: 105. Construct Binary Tree from Preorder and Inorder Traversal

The Problem Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree. Example Input: preorder = [3,9,20,15,7], inorder = [9,3,15,20,7] Output:

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LeetCode: 103. Binary Tree Zigzag Level Order Traversal

The Problem Given the root of a binary tree, return the zigzag level order traversal of its nodes' values. (i.e., from left to right, then right to left for the next level and alternate between). Example Input: [3,9,20,null,null,15,7] Output: [[3],[20,9]

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LeetCode: 102. Binary Tree Level Order Traversal

The Problem Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level). Example Input: [3,9,20,null,null,15,7] Output: [[3],[9,20],[15,7]] Constraints: * The number of nodes in the

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LeetCode: 99. Recover Binary Search Tree

The Problem You are given the root of a binary search tree (BST), where the values of exactly two nodes of the tree were swapped by mistake. Recover the tree without changing its structure. Example Input: [1,3,null,null,2] Output: [3,1,null,null,2] Explanation: 3 cannot

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LeetCode: 98. Validate Binary Search Tree

The Problem Given the root of a binary tree, determine if it is a valid binary search tree (BST). A valid 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

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LeeCode: 96. Unique Binary Search Trees

The Problem Given an integer n, return the number of structurally unique BST's (binary search trees) which has exactly n nodes of unique values from1ton. Example n = 3 Input: n = 3 Output: 5 Constraints: * 1 <= n <= 19 The solution We initially implemented the calculation of Catalan

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LeetCode: 95. Unique Binary Search Trees II

The Problem Given an integer n, return all the structurally unique BST's (binary search trees), which has exactly n nodes of unique values from1ton. Return the answer in any order. Example N = 3 Input: n = 3 Output: [ [1,null,2,null,3], [1,null,3,2], [2,1,

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LeetCode: 2331. Evaluate Boolean Binary Tree

The Problem You are given the root of a full binary tree with the following properties: * Leaf nodes have either the value 0 or 1, where 0 represents False and 1 represents True. * Non-leaf nodes have either the value 2 or 3, where 2 represents the boolean OR and 3

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LeetCode: 2236. Root Equals Sum of Children

The Problem You are given the root of a binary tree that consists of exactly 3 nodes: the root, its left child, and its right child. Return true if the value of the root is equal to the sum of the values of its two children, or false otherwise. Example

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LeetCode: 1379. Find a Corresponding Node of a Binary Tree in a Clone of That Tree

The Problem Given two binary trees original and cloned and given a reference to a node target in the original tree. The cloned tree is a copy of the original tree. Return a reference to the same node in the cloned tree. Note that you are not allowed to change

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LeetCode: 1022. Sum of Root To Leaf Binary Numbers

The Problem You are given the root of a binary tree where each node has a value 0 or 1. Each root-to-leaf path represents a binary number starting with the most significant bit. * For example, if the path is 0 -> 1 -> 1 -> 0 -&

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LeetCode: 993. Cousins in Binary Tree

The Problem Given the root of a binary tree with unique values and the values of two different nodes of the tree x and y, return true if the nodes corresponding to the values x and y in the tree are cousins, or false otherwise. Two nodes of a binary

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LeetCode: 965. Univalued Binary Tree

The Problem A binary tree is uni-valued if every node in the tree has the same value. Given the root of a binary tree, return true if the given tree is uni-valued, or false otherwise. Example Input: [2,2,2,5,2] Output: false Constraints: * The number of nodes in

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LeetCode: 897. Increasing Order Search Tree

The Problem Given the root of a binary search tree, rearrange the tree in in-order so that the leftmost node in the tree is now the root of the tree, and every node has no left child and only one right child. Example Input: [5,1,7] Output: [1,null,

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LeetCode: 783. Minimum Distance Between BST Nodes

The Problem Given the root of a Binary Search Tree (BST), return the minimum difference between the values of any two different nodes in the tree. Example Input: [4,2,6,1,3] Output: 1 Constraints: * The number of nodes in the tree is in the range [2, 100]. * 0

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LeetCode: 700. Search in a Binary Search Tree

The Problem You are given the root of a binary search tree (BST) and an integer val. Find the node in the BST that the node's value equals val and return the subtree rooted with that node. If such a node does not exist, return null. Example Input:

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LeetCode: 671. Second Minimum Node In a Binary Tree

The Problem Given a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactly two or zero sub-node. If the node has two sub-nodes, then this node's value is the smaller value among its two sub-nodes. More formally, the

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LeetCode: 653. Two Sum IV - Input is a BST

The Problem Given the root of a binary search tree and an integer k, return trueif there exist two elements in the BST such that their sum is equal tok, orfalseotherwise. Example Input: root = [5,3,6,2,4,null,7], k = 9 Output: true Solution We adopted a inorder

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LeetCode: 637. Average of Levels in Binary Tree

The Problem Given the root of a binary tree, return the average value of the nodes on each level in the form of an array. Answers within 10-5 of the actual answer will be accepted. Example Input: [3,9,20,null,null,15,7] Output: [3.00000,14.50000,11.

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LeetCode: 617. Merge Two Binary Trees

The Problem You are given two binary trees root1 and root2. Imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not. You need to merge the two trees into a new binary tree. The merge

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LeetCode: 606. Construct String from Binary Tree

The Problem Given the root of a binary tree, construct a string consisting of parenthesis and integers from a binary tree with the preorder traversal way, and return it. Omit all the empty parenthesis pairs that do not affect the one-to-one mapping relationship between the string and the original binary

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LeetCode: 572. Subtree of Another Tree

The Problem Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false otherwise. A subtree of a binary tree tree is a tree that consists of a node in tree

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LeetCode: 563. Binary Tree Tilt

The Problem Given the root of a binary tree, return the sum of every tree node's tilt. The tilt of a tree node is the absolute difference between the sum of all left subtree node values and all right subtree node values. If a node does not have

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LeetCode: 543. Diameter of Binary Tree

The Problem Given the root of a binary tree, return the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root. The length