228 interactive lessons · 4,629 quiz questions

See algorithmsthink.

Algorithms, system design, machine learning, databases and AI engineering — every idea as a live visualization you can pause, rewind and break. Then prove you got it.

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Takes two minutes. No account needed to start.

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Open the full Quick Sort lesson — step through it, then take the quiz

Try it: pick an algorithm, shuffle, sort. This is a real lesson, running.

Arrays & ListsGraph Coloring (Greedy)A* SearchTwo Pointers TechniqueBinary SearchAdvanced Binary Search PatternsMinimum Spanning Tree (Kruskal's Algorithm)Probability Distributions 3DNaive Bayes ClassifierPrecision/Recall Trade-off & PR vs ROCK-Means Clustering 3DBackpropagationCNN Architecture (Full Pipeline)Text Representation (OHE, BOW, N-gram, TF-IDF, Word2Vec)Regularization in Weight Space 3DConvNetJS CIFAR-10Client-Server ModelTCP 3-Way Handshake

What are you here for?

Pick one and answer two or three quick questions. We'll place you at the right point in a learning path.

I'm preparing for coding interviewsPatterns, data structures and system design, with questions to practise on.I'm learning data structures and algorithms from scratchBig-O, arrays and linked lists first, then sorting, trees, graphs and DP.I'm learning system designThe interview method, networking basics, caches, queues, databases and full designs.I'm learning ML or AI engineeringBuild with LLMs (RAG, agents, evals) or train and ship your own models.

Or jump into a topic

DSA System Design Databases Machine Learning Deep Learning AI Engineering ML Systems Design Sorting algorithms Graph algorithms Dynamic programming Coding interview patterns LLMs and transformers

01 / 0548 visualizations · ~18 h

Algorithms

Sorts, graphs, trees and dynamic programming, run one operation at a time with the code highlighted beside them.

Browse Algorithms

Sorting25 of 26 placedO(n log n)

How a lesson works

Watch it.
Predict it.
Prove it.

Understanding is the moment you can say what happens next before it does. Every lesson is built around that moment. Try the one on the right.

01 Watch

Every lesson runs on a transport bar. Pause on any step, go back one, change the input and run it again.

02 Predict

Quick sort has just dropped its pivot into place. What is true of every element to its left?

03 Prove

Write it yourself in the in-browser editor. Hidden tests decide when you are done.

sorts an empty array
keeps duplicates
handles sorted input
handles negative numbers

Pick a path

From zero, in the right order.

Each path sequences the lessons into phases, and every phase ends in a capstone you build and can show an interviewer.

Your first lesson takes two minutes.

Every visualization and every quiz is free. Start now, make an account later to keep your streak.

Start learning See the paths

lessons: 228; lessons
quiz questions: 4,629; quiz questions
career paths: 3; career paths