Leetcode Solutions

Question 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 1: Input: root = [4,2,7,1,3], val = 2 Output: [2,1,3] Example 2: Input: root = […]

Question You are keeping the scores for a baseball game with strange rules. At the beginning of the game, you start with an empty record. You are given a list of strings operations, where operations[i] is the ith operation you must apply to the record and is one of the following: An integer x. Record a new score of x. ‘+’. Record

Question There is a robot starting at the position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it completes its moves. You are given a string moves that represents the move sequence of the robot where moves[i] represents its ith move. Valid moves are ‘R’ (right), ‘L’ (left), ‘U’ (up), and ‘D’ (down). Return true if the robot returns

Question You are given an integer array nums with no duplicates. A maximum binary tree can be built recursively from nums using the following algorithm: Create a root node whose value is the maximum value in nums. Recursively build the left subtree on the subarray prefix to the left of the maximum value. Recursively build the right subtree on the subarray suffix to the right of the maximum value. Return the maximum

Question Given the root of a Binary Search Tree and a target number k, return true if there exist two elements in the BST such that their sum is equal to the given target. Example 1: Input: root = [5,3,6,2,4,null,7], k = 9 Output: true Example 2: Input: root = [5,3,6,2,4,null,7], k = 28 Output: false Constraints: The number of

Question 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 1: Input: root = [3,9,20,null,null,15,7] Output: [3.00000,14.50000,11.00000] Explanation: The average value of nodes on level 0 is 3, on level 1 is 14.5, and on

Question Table: Salary +————-+———-+ | Column Name | Type | +————-+———-+ | id | int | | name | varchar | | sex | ENUM | | salary | int | +————-+———-+ id is the primary key for this table. The sex column is ENUM value of type (‘m’, ‘f’). The table contains information about an

Question Table: Cinema +—————-+———-+ | Column Name | Type | +—————-+———-+ | id | int | | movie | varchar | | description | varchar | | rating | float | +—————-+———-+ id is the primary key for this table. Each row contains information about the name of a movie, its genre, and its rating. rating

Question Given the root of an n-ary tree, return the postorder traversal of its nodes’ values. Nary-Tree input serialization is represented in their level order traversal. Each group of children is separated by the null value (See examples) Example 1: Input: root = [1,null,3,2,4,null,5,6] Output: [5,6,3,2,4,1] Example 2: Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14] Output: [2,6,14,11,7,3,12,8,4,13,9,10,5,1] Constraints: The number of

Question Table: World +————-+———+ | Column Name | Type | +————-+———+ | name | varchar | | continent | varchar | | area | int | | population | int | | gdp | int | +————-+———+ name is the primary key column for this table. Each row of this table gives information about the name