HackerRank is a place where programmers from all over the world come together to solve programming problems. It provides verified solutions you can check at any time and a wide array of programming/coding questions for you to solve.
2. Exercism IO
Codewars provides you with ‘kata’ challenges focused on improving skill and technique. Some train programming basics, while others focus on complex problem-solving. They also provide puzzles meant to test your creative problem-solving.
This platform provides a list of algorithmic challenges from the past that you can complete on your own directly online. At TopCoder, you can compete with other programmers as well.
Leetcode is an interview-based Platform where programming questions are asked directly, to help you prepare for your job interview. Their questions are based on 9 programming languages.