All coding competitions & hackathons

Coding challenges include a plethora of competitions like hackathons, programming challenges, and more. They are aimed at challenging your coding skills. Hackathons generally include developing an app/game/website based on a particular theme. Whereas programming challenges are time-bound activities that need participants to solve coding problems in a stipulated time.

Coding competitions are aimed at testing your coding skills. They help in developing problem solving skills, cognitive functioning, logical thinking, and programming skills.

For beginner coders - Codingal, Google Kickstart, CodeWars
For intermediate coders - CodeFight, CodinGame, Codingal
For advanced coders - CodeChef, TopCoder, HackerRank

Participating in coding competitions helps you come across a variety of coding problems based on data structures and algorithms. The more you practice and rank in these competitions it will help you increase your speed and accuracy to solve problems in the qualifying competitions for IOI.