1. Problem Summary You are given an integer array nums. Your task is to partition the array into two contiguous parts: such that: You must return the smallest possible size of left, meaning the smallest index i + 1. Example: 2. Key Insights Insight 1: Left must contain all values up to its max For…

1. Problem Summary You are given an unsorted integer array nums. Your task is to find the length of the longest consecutive sequence, where: Example: 2. Key Insights Insight 1: Sorting works, but too slow Sorting takes: But we need an O(N) solution. Insight 2: HashSet enables O(1) lookups If values are stored in a…

1. Problem Summary You are given a 2D grid consisting of: An island is defined as a group of connected 1s where connectivity is: Your task is to compute: If there is no land at all, return: Example: 2. Key Insights Insight 1: This is a connected-component counting problem Each island is a connected region…

1. Problem Summary You are given an array of strings words. Your task is to find the maximum value of: where: Example: Valid pair: Lengths: Output: 2. Key Insights Insight 1: Checking shared letters directly is too slow Naive comparison of characters between every pair is: Where L = max word length. Insight 2: Letters…

1. Problem Summary You are given a string n representing a positive decimal integer.Your task is to determine the minimum number of positive deci-binary numbers whose sum equals n. A deci-binary number is defined as: Goal: Example: 2. Key Insights Insight 1: Digits add independently by position Since deci-binary numbers only contain 0 or 1…

1. Problem Summary You are given the root of a binary tree.Your task is to return the level order traversal, meaning: Example interpretation: Given tree: Output: 2. Key Insights Level order traversal is essentially a breadth-first traversal We must explore the tree breadth-first rather than depth-first. A queue naturally processes nodes level by level As…

1. Problem Summary You are given an integer array nums. Your task is to determine whether the array can become non-decreasing by modifying at most one element. A non-decreasing array satisfies: Constraints and rules: Example: Example: 2. Key Insights Insight 1: Violations tell the story A violation occurs when: If we encounter more than one…

1. Problem Summary You are given an integer array nums, and your task is to determine whether it is possible to make the array non-decreasing by modifying at most one element. A non-decreasing array satisfies: Rules: Example interpretation:Input: Modify 4 → 2 to get [2,2,3] → return true. Input: Needs at least two modifications →…

1. Problem Summary You are given an integer array nums. Your task is to compute and return a new array result where: This is known as the running sum or prefix sum of the array. Example interpretation:If: Then: 2. Key Insights Running sum accumulates progressively Each position builds on previous sum rather than recomputing from…

1. Problem Summary You are given the head of a singly linked list.Your task is to determine whether the linked list represents a palindrome, meaning: Important details: Example interpretation:Input: Output: Another example: Output: 2. Key Insights Linked lists do not allow reverse indexing Unlike arrays, we cannot compare front and back via indices efficiently. Optimal…