Array

The O(n) Club: Shortest Unsorted Subarray — Only Sort What’s Broken ⚡ TL;DR Given an array of integers, find the length of the shortest…

The O(n) Club: K Closest Points to Origin—Or, How to Avoid a Heap of Regret ⚡ TL;DR Don’t overthink it: Want the k closest 2D points to (0,…

The O(n) Club: N-Queens Without The Emotional Damage ⚡ TL;DR Need to park N queens on an N×N chessboard with zero drama? They can’t…

The O(n) Club: Insert Delete GetRandom O(1) — The Data Structure That Won’t Waste Your Time ⚡ TL;DR Set with insert, delete, and…

The O(n) Club: Find Peak Element — Java’s Favorite Uphill Battle ⚡ TL;DR Need a peak in your int[]? Just look for any nums[i] that’s bigger…

The O(n) Club: Count of Smaller Numbers After Self (or, Why Timing Out Is a Lifestyle Choice) ⚡ TL;DR For each number in your array, count how…

The O(n) Club: 3Sum Closest – When Close Enough Is As Good As It Gets ⚡ TL;DR Don’t go all-in on O(n³) brute force unless you love noise…

The O(n) Club: Climbing Stairs Without Emptying Your Wallet (LeetCode 746) ⚡ TL;DR The stairs want your money—but you’re smarter than that.…

The O(n) Club: Max Area of Island — Because DFS Is Land Lord ⚡ TL;DR You get a grid of 0s (water) and 1s (land). Your mission, should you…

The O(n) Club: Best Time to Buy and Sell Stock III — Survive the Two-Trade Gauntlet ⚡ TL;DR Buy, sell, buy, sell—can you time these two trades…