Reference

Big O basicsWhat the notation means, a growth playground, and how to read the tables.
Data structuresArrays, hash tables, trees, heaps, tries, Union-Find, and graph representations.
SortingBest, average, and worst case for 13 sorts, with the footnotes that matter.
Search and graphsBinary search, BFS, DFS, heaps, shortest paths, and spanning trees.
Coding patternsTypical costs of two pointers, sliding window, backtracking, and DP.

Tools

Complexity lookupBest, average, and worst case for one operation, with its caveat.
Compare two algorithmsTime, space, stability, and trade-offs side by side.
VisualizerStep through searches, four sorts, BFS, and DFS one move at a time.
Export and shareMarkdown, CSV, printable cards, and PDFs.

Practice

RoadmapA suggested order for the topics, with prerequisites and progress.
QuizTen random questions with an explanation after each answer.
Code challengesPredict the time and space of short snippets in three languages.
Revision sheetThe high-relevance topics on one printable page.

Practice

Code complexity challenges

Read the snippet, then predict both its time and its auxiliary space before you reveal the answer. Snippets are shown in Python, JavaScript, and Java. Costs can differ between languages, and the explanation says when they do.

BigOSheet

A Big O reference for interview prep. Every bound says which case it is and what it assumes.

Full PDF · One-page PDF

Reference

All topics
Big O basics
Data structures
Sorting
Search and graphs
Coding patterns

Tools

Complexity lookup
Compare two algorithms
Visualizer
Export and share

Practice

Roadmap
Quiz
Code challenges
Revision sheet

Made by Aryan Kumar. MIT license. Source and corrections on GitHub.Progress stays in this browser. ?

Keyboard shortcuts

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r: Open the revision sheet
b: Save or unsave the focused card, or the topic you are reading
l: Mark the focused card, or the topic you are reading, as learned
Space Left arrow Right arrow: In the visualizer: play or pause, step back, step forward
1 to 4 Enter: In the quiz: pick an answer, then go to the next question
Escape: Close this list