Watch algorithms think.
Learn data structures and algorithms by stepping through them, one small move at a time, until the patterns feel familiar.
go on, step it yourself Press → or ▶
Getting the demo ready…
How it works
Every lesson follows the same three moves.
1Watch
Step through real algorithms one move at a time, with a plain sentence for every step.
2Predict
Guess the next move before it plays and get instant feedback. A wrong guess teaches you the rule.
3Practice
Try your own input and watch the same algorithm run on it. Then take on real LeetCode problems.
Choose a path
Start at the beginning, or jump to what you need. Each path is a short run of lessons.
Path
Foundations
7 lessons
Start here. How data sits in memory, and why that makes some operations instant and others slow.
Explore FoundationsPath
Core Patterns
7 lessons
The handful of moves behind most array and string problems. Learn to spot which one a problem wants.
Explore Core PatternsPath
Recursion, Trees & Graphs
7 lessons
Think recursively, then walk branching structures: trees, heaps, tries and graphs.
Explore Recursion, Trees & GraphsPath
Optimization
2 lessons
When brute force is too slow: make the safe greedy choice, or remember answers to smaller problems.
Explore Optimization
Spot the pattern
Read a problem, name the pattern it wants. Short drills that train the one skill interviews test.
Your first lesson takes about 25 minutes.
Nothing to install and no account. Just open it and press play.
Start with Arrays