Understand
Begin with a plain-language mental model and a concrete problem.
Free and open learning
Algorithms should be understood, not memorized.
Explore algorithms through interactive visualizations, working code, guided examples, and small challenges—freely available to every learner.
Our learning promise
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Knowledge grows when it is shared.
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Available lessons
8 complete lesson · 4 on the roadmap
01Open lesson →02Open lesson →03Open lesson →04Open lesson →05Open lesson →06Open lesson →07Open lesson →08Open lesson →
sortingBeginner
Bubble Sort
Compare adjacent values and watch the largest unsorted item rise into place.
JavaScript + Python + Java + C++O(n²) averageVisualizer + game
sortingBeginner
Selection Sort
Find the smallest remaining value and place it at the next sorted position.
JavaScript + Python + Java + C++O(n²) averageVisualizer + game
sortingBeginner
Insertion Sort
Take the next value and shift larger sorted values right until it fits.
JavaScript + Python + Java + C++O(n²) averageVisualizer + game
sortingIntermediate
Merge Sort
Divide values into smaller arrays, sort them, and merge the ordered results.
JavaScript + Python + Java + C++O(n log n) averageVisualizer + game
sortingIntermediate
Quick Sort
Partition values around a pivot, then recursively sort the two resulting ranges.
JavaScript + Python + Java + C++O(n log n) averageVisualizer + game
sortingIntermediate
Heap Sort
Build a max heap and repeatedly extract its largest value.
JavaScript + Python + Java + C++O(n log n) averageVisualizer + game
sortingIntermediate
Counting Sort
Count bounded integer values instead of comparing pairs.
JavaScript + Python + Java + C++O(n + k) averageVisualizer + game
sortingIntermediate
Radix Sort
Order integer keys one digit position at a time.
JavaScript + Python + Java + C++O(d(n + b)) averageVisualizer + game
The method
Learn with four connected steps
Every lesson follows the same path, so you can focus on the idea rather than relearning the interface.
Visualize
Move through every comparison, choice, state change, and result.
Implement
Compare tested JavaScript, Python, Java, and C++ implementations.
Practice
Use examples, challenges, and games to make the idea stick.
The roadmap
Explore by category
One growing library, organized around the way algorithmic thinking develops.
Sorting
Arrange data and compare different strategies for ordering it.
8 planned8 available
Searching
Find values efficiently in lists, ranges, and structured data.
1 plannedComing soon
Graphs
Explore networks, paths, traversal, and shortest-route problems.
2 plannedComing soon
Recursion
Break problems into smaller versions of themselves.
— plannedComing soon
Dynamic programming
Reuse solved subproblems to make difficult problems tractable.
1 plannedComing soon
Greedy
Build solutions through locally optimal choices.
— plannedComing soon
Strings
Match, search, transform, and reason about text efficiently.
— plannedComing soon
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Open to contributors.
Algorithm Lab has no sign-in gate, paid tier, or locked lesson. The source code is open, the study material is reusable with attribution, and contributions are welcome.