Array

The O(n) Club: Reverse Pairs & That Merge Sort Plot Twist ⚡ TL;DR LeetCode 493 asks: How many index pairs (i, j) have i 2 * nums[j]?Brute…

The O(n) Club: Maximum Product of Three Numbers — Beware the Negative Numbers Plot Twist ⚡ TL;DR Want the biggest product from any three…

The O(n) Club: Number of Islands — Why Diagonal Swimming Doesn’t Count ⚡ TL;DR Given a grid of ‘1’s (land) and…

The O(n) Club: Wiggle Subsequence — Try Not To Flatline ⚡ TL;DR Find the length of the longest up-down-up-down (no meh in the middle)…

The O(n) Club: Jump Game III – Exactly, Unforgivingly, To Zero (Or Die Trying) ⚡ TL;DR You’re stuck in an array where each index is a dramatic…

The O(n) Club: Sort Array By Parity — When Evens Take the Lead (and Odds Wait in Line) ⚡ TL;DR You want all the even numbers at the start and…

The O(n) Club: Spiral Matrix II — Mastering The Swirly-Square Algorithm Without Losing Your Sanity ⚡ TL;DR Fill an n x n grid in spiral order…

The O(n) Club: Subarray Sums Divisible by K (Now with Fewer Caffeine-Induced Tears) ⚡ TL;DR Want to know how many subarrays have sums…

The O(n) Club: Minimum Number of Arrows to Burst Balloons Without Losing (Your Mind) ⚡ TL;DR This is LeetCode 452, not the Macy’s…

The O(n) Club: Trapping Rain Water II — How to Flood a 2D Matrix Without Crying ⚡ TL;DR This is the classic LeetCode problem where you…