Codeforces

LeetCode is the most popular platform for practicing coding problems, preparing for technical interviews, and improving algorithm skills.

HackerRank offers coding challenges and competitions for learning programming, algorithms, data structures, and interview prep.

CodeChef is a competitive programming platform hosting contests, practice problems, and a learning community for programmers.

GeeksforGeeks is a comprehensive learning platform for programming, algorithms, data structures, and interview preparation.

InterviewBit helps you prepare for coding interviews with curated problems, mock interviews, and company-specific prep materials.

TopCoder is one of the first competitive programming platforms offering contests, challenges, and freelance opportunities for developers.