Array

The O(n) Club: Surrounded Regions — Don’t Flip Out, Mark the Borders! ⚡ TL;DR Got a board of ‘O’s and ‘X’s? Flip every…

The O(n) Club: Sudoku Solver—Backtracking Without Losing Your Sanity ⚡ TL;DR Solve Sudoku like you mean it—skip brute force, do backtracking!…

The O(n) Club: Gas Station — Why Your Algorithm’s Tank Keeps Running Empty ⚡ TL;DR Need to drive around a circle of gas stations without…

The O(n) Club: Single Element in a Sorted Array — When XOR Won’t Save You ⚡ TL;DR Given a sorted array where every element appears twice…

The O(n) Club: Coin Change 2 — Counting Combos, Not Coins (Because Life’s Complicated Enough) ⚡ TL;DR Count the number of ways to make a given…

The O(n) Club: Pascal’s Triangle — Why Is Everything a 1? ⚡ TL;DR Pascal’s Triangle is that legendary integer pyramid where each number…

The O(n) Club: House Robber II—When Your Path Turns Circular (and Paranoid) ⚡ TL;DR Old problem: Rob a line of houses, don’t trip two neighbor…

The O(n) Club: Evaluate Division – Connect the Dots, Multiply the Drama ⚡ TL;DR Take some equations like a / b = 2.0, make a directed,…

The O(n) Club: Missing Number — How to Outsmart That One Number Who Didn’t RSVP ⚡ TL;DR One number from to n ditched your array —…

The O(n) Club: Queue Reconstruction by Height is Just Tall-Tale Sorting ⚡ TL;DR You get a list of [height, k] for people—k means “number of…