#contests

atcoder.jp

AtCoder is a premier competitive programming platform that hosts regular online contests for developers and students of all skill levels. It offers a variety of algorithm and heuristic challenges to help users improve their coding and problem-solving abilities.

codeforces.com

A premier competitive programming platform hosting regular algorithmic contests, a global user rating system, and an extensive problem archive. It serves as a central hub for developers to practice coding skills and engage with a global community.