codeforces. programming competitions and contests, programming community

start your coding journey with our expert-designed, job-focused practical coding courses. learn to code from scratch with interactive, beginner-friendly lessons.

hackerrank is the market-leading technical assessment and remote interview solution for hiring developers. learn how to hire technical talent from anywhere!

a website dedicated to the fascinating world of mathematics and programming

the goal of this project is to translate the wonderful resource http://e-maxx.ru/algo which provides descriptions of many algorithms and data structures especially popular in field of competitive programming. moreover we want to improve the collected knowledge by extending the articles and adding new articles to the collection.

stack overflow is the largest, most trusted online community for developers to learn, share​ ​their programming ​knowledge, and build their careers.

learn to code — for free

atcoder is a programming contest site for anyone from beginners to experts. we hold weekly programming contests online.

github is where over 100 million developers shape the future of software, together. contribute to the open source community, manage your git repositories, review code like a pro, track bugs and features, power your ci/cd and devops workflows, and secure code before you commit it.

well organized and easy to understand web building tutorials with lots of examples of how to use html, css, javascript, sql, python, php, bootstrap, java, xml and more.