Coding interview problems
224 problems. Filter by topic or difficulty, then solve one in your browser.
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The courses most Coddy learners take.
Web
Build websites and web apps, from the first tag to React.
Next.jsNewProgramming languages
General-purpose languages for apps, scripts and backends.
Systems & hardware
Get close to the machine: memory, chips and smart contracts.
Mobile apps
Build apps for iPhone and Android.
Games
Make your own games in Roblox, Unity and Godot.
Data & AI
Query, analyze and chart data, and put AI to work.
Tools & DevOps
The command line and the tools every developer works with.
Math
View all →From arithmetic to trigonometry, worked out step by step.
Physics
View all →Physics from forces to gravity, solved step by step.
Chess
View all →From the rules to tactics, checkmates and endgames.
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DocsReference documentation for every supported language.PlaygroundWrite and run code in the browser, no setup required.ToolsFree utilities for developers: formatters, converters, and more.Embed EditorAdd a free, runnable code editor to your own site with one iframe.Cheat SheetsQuick-reference tables for the languages and tools you use.GlossaryPlain definitions of programming terms, each with a runnable example.Interview ProblemsCoding interview problems you can run in the browser, with hints.Interview QuestionsQuestions with short answers, runnable code and output quizzes.Git CommandsEvery Git command you reach for, with syntax, flags, and examples.VisualizationsWatch algorithms and data structures run step by step.
Play vs ComputerSix bots from beginner to master, plus pass-and-play. Free, with a coaching review.ToolsInteractive boards and references you can try in place.ConceptsEvery rule and tactic explained on a board you play it on.OpeningsEvery opening on a board you play: the main line, the plans, the traps.PuzzlesA daily puzzle and mate in 1, 2 and 3 sets.
AboutLearn what Coddy is and the team behind it.BlogTutorials, guides, and stories from the Coddy team.Bugsy, the AI tutorReads your code and your error, explains, and hints. Never the answer.CertificationsEarn shareable certificates by completing courses.ContactGet in touch with support, partnerships, or press.PressQuick facts, founder bios, and the press contact.BrandLogo, colors, fonts, voice, and our characters Bit and Bugsy.CareersOpen roles, our mission, and what it’s like to work at Coddy.TeachersCoddy for teachers: assign lessons, track progress, and grade automatically.AffiliatePromote Coddy and earn commissions on referrals.Mobile AppLearn to code on iPhone and Android, free on both stores.Coddy Build
Build full-stack apps with AI: chat, preview, and publish.
Build full-stack apps with AI: chat, preview, and publish.Coddy