AtCoder is a programming contest site for beginners to experts.

Learn to code for free using our beginner friendly and interactive learning courses. Get all the practical skills required to excel at computer science.

Codeforces is a website for practicing competitive programming

Want to participate in coding wars? Compete with other coders worldwide by participating in the contests. You also earn points for your achievements.

This website is the best place to practice programming problems, review company interview questions, and improve your coding skills

This resource provides developers with competitive programming challenges to improve their skills in multiple languages. It also allows tech recruiters to assess developers on their problem-solving skills.

This site offers competitive coding challenges and interview preparation resources for software engineers and developers.

SPOJ is an online judge system with over 315,000 registered users and over 20,000 problems.