Array

The O(n) Club: Rotate Array—The Triple Reverse Shuffle You Secretly Hate ⚡ TL;DR Rotate your array to the right by k steps. Don’t copy…

The O(n) Club: Preorder-Inorder Tree Rebuilds — Actually Fun, Actually Linear ⚡ TL;DR Want to turn two scrambled traversals back into a…

The O(n) Club: Rotate Image Without Losing Your Mind (LeetCode 48) ⚡ TL;DR Rotate your n x n matrix 90° in-place by: (1) transposing (swap…

The O(n) Club: Majority Element — The Array’s Unbeatable Bully ⚡ TL;DR The Majority Element is the number that turns your array into a…

The O(n) Club: Move Zeroes — In-Place, In-Order, In-Interview Panic ⚡ TL;DR Move all zeroes to the end of your array—don’t use extra space,…

The O(n) Club: Kth Largest Java Throwdown (Why Sorting Alone Won’t Save You) ⚡ TL;DR If you’re after the Kth largest element in a…

The O(n) Club: Subsets (Power Set): Why Your Algorithmic FOMO Is Actually Required ⚡ TL;DR You need every possible subset of a set of unique…

The O(n) Club: Longest Consecutive Sequence — Arrays, Coffee, and Why HashSets Are Your Real Friends ⚡ TL;DR Unsorted array, need the longest…

The O(n) Club: Word Search – When DFS Meets a Letter Maze ⚡ TL;DR Take a grid of letters, try to trace your chosen word by hopping between…

The O(n) Club: First Missing Positive—That Sneaky Little Integer You Forgot ⚡ TL;DR Your dev lead wants the smallest missing positive integer…