Array

The O(n) Club: Accounts Merge — When Emails Collide, but Names Are Lying ⚡ TL;DR If two user accounts share an email, guess what?…

The O(n) Club: Next Greater Element II—When Arrays Forget Where Home Is ⚡ TL;DR Find the next greater number for each element in a circular…

The O(n) Club: 01 Matrix — Why BFS Always Gets the Invite (and DFS Sits Out) ⚡ TL;DR The mission: For every 1 in your binary grid, find the…

The O(n) Club: Island Perimeter — Don’t Forget to Subtract the Neighbors ⚡ TL;DR Calculate the perimeter of a single “island”…

The O(n) Club: How to Actually Rebuild a Binary Tree from Inorder and Postorder (Without Crying) ⚡ TL;DR Given two arrays (inorder,…

The O(n) Club: Minimum Cost for Tickets (aka, The ‘Why Can’t I Just Be Greedy’ Problem) ⚡ TL;DR Given a random set of travel…

The O(n) Club: Majority Element II and the Pigeonhole Plot Twist ⚡ TL;DR Need to spot every array element that appears more than n/3 times?…

The O(n) Club: Why Splitting Arrays Feels Like Filing Taxes (LeetCode 410 Explained) ⚡ TL;DR You’ve got a rowdy array, and you want to…

The O(n) Club: Unique Subsets With Twins (How to Uninvite Duplicate Guests) ⚡ TL;DR Need to find every combo of numbers in an array (even if…

The O(n) Club: Unique Paths II—Help, My Robot Can’t Even (LeetCode 63 Edition) ⚡ TL;DR You’re coding a grid-crawling robot, but…