AlgoFoxGet AlgoFox App

CoursesArray PatternsSliding Window

Boss: Minimum Window Substring

The island's final exam: cover every character of t — duplicates included — with the shortest stretch of s, using an expand-then-shrink window and a need counter for O(1) coverage checks.

BossComplete codeDebugCode orderMultiple choiceTrace8 exercises, 10 min
AlgoFox Pro

Array Patterns is part of AlgoFox Pro

You can read the whole course outline here. The exercises are in the app, along with your streak, your mistake review, and the progress that carries across your devices.

Pro starts with a 3 day free trial. The app store decides who is eligible for an introductory offer, and a lapsed subscription does not get another one.

Download AlgoFox on the App StoreGet AlgoFox on Google Play

Already subscribed in the app? Sign in with the same account and Pro works here too. Quick Play and Battle are free on the web, and so is the first course in every subject.