Improve your skills by solving real coding problems. Write code, submit, and get instant feedback. 122 practice problems per language · 12 languages Alternating Sum Add and subtract numbers in turn. Subscribe to Weekly Practice Problem Get the latest coding practice problem delivered to your inbox every week. Select a Language General-purpose, beginner-friendly language. Object-oriented, widely used in enterprise. Low-level systems programming language. Powerful language for performance-critical apps. Modern language for .NET and game development. Server-side scripting for web development.

Modern language for Android and JVM. The language of the web. Runs in Node.js. Typed JavaScript for larger applications. Apple's language for iOS and macOS apps. Safe, fast systems programming language. Statistical computing and data analysis. Each challenge gives you a problem description and starter code in an online editor. Your program reads input and prints the correct output. When you submit, your code is tested against multiple hidden test cases with different inputs. Your score is the percentage of tests passed. Pass all tests to earn full XP. Partial credit is given for partially correct solutions. W3Schools Adventure App Coding fundamentals as a game. Bite-sized lessons and challenges. If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: sales@w3schools.com If you want to report an error, or if you want to make a suggestion, send us an e-mail: help@w3schools.com