Google Code Jam
Google's yearly online algorithm contest
Google Code Jam was a yearly online contest of algorithm problems. You started with a qualification round, moved through timed online rounds, and the best players reached the World Finals. You could use any programming language.
2003–2023 · Contest
About Google Code Jam
Google ended the contest in 2023. Logins stopped on 1 June 2023, and the contest site shut down on 1 July 2023.
You can still practice with the old problems. Google keeps an official archive on GitHub with statements, analyses, test data and judging code from Code Jam, Kick Start and Hash Code. There is no live judge, so you check your answers yourself against the test data. The problems are hard and suit experienced competitive programmers.