Problem Summary You are given an integer array nums. You must choose three indices i < j < k such that the value is maximized. Return the maximum possible value of this expression. Constraints Understanding the Expression We want to maximize: The constraints are: Important Observations If (nums[i] – nums[j]) is negative, multiplying with positive…

Problem Summary You are given a 2D array questions, where each entry is: If you solve question i: If you skip question i, you earn nothing and simply move to the next one. Your task is to compute the maximum points you can earn. ExampleInput: Output: Explanation:You can solve question 0 (earn 3), then must…

Problem Summary You are given an n x n binary grid where: You may change at most one 0 to 1. Your task is to return the size of the largest island you can achieve after performing at most one such change. An island is a group of 1s connected 4-directionally. ExampleInput: Output: 3 Explanation:Turning…

Problem Summary Given an integer array nums, return the length of the longest strictly increasing subsequence (LIS). A subsequence does not need to be contiguous, but must keep the original order. ExampleInput: nums = [10, 9, 2, 5, 3, 7, 101, 18]Output: 4Explanation: A possible LIS is [2, 3, 7, 18]. Input: nums = [0,…

Problem Summary You are given an array of pairs, where each pair is a two-element array [a, b]. A pair [a, b] can be chained with [c, d] if and only if: Your task is to find the maximum length of a chain you can form. ExampleInput: [[1,2], [2,3], [3,4]]Output: 2Explanation: You can form the…

Problem Summary You are given a string s and an integer k. You can perform the following operation any number of times: Your task is to return the lexicographically smallest string you can obtain after applying any number of operations. ExamplesInput: s = “cba”, k = 1Output: “acb” Input: s = “baaca”, k = 3Output:…

Problem Summary You are given the root of a binary tree.Your task is to determine whether the tree is a valid Binary Search Tree (BST). A valid BST must satisfy: ExampleInput: Output: true Input: Output: falseReason: The right subtree contains 3, which is not greater than 5. Approach 1: Recursion Using Min/Max Boundaries (Most Common…

Problem Summary This is an interactive problem.You are given a secret word chosen from a list of unique words.Each word has exactly 6 lowercase letters. You do not know which word is the secret word, but you can call: This function returns the number of positions where the guessed word matches the secret word exactly.…

Problem Summary You are given the root of a Binary Search Tree (BST) and an integer k.Your task is to determine whether there exist two distinct nodes in the tree whose values sum to k. Return true if such a pair exists; otherwise return false. Example BST: Example queries:For k = 9, output is true…

Problem Summary You are given an integer array nums and an integer target.Your task is to find three distinct integers in the array such that their sum is closest to target.Return that sum. There is guaranteed to be exactly one solution. ExampleInput: nums = [-1, 2, 1, -4], target = 1Output: 2Explanation: The closest sum…