Competitive 10 specimens

Algorithmic sport and skill sharpening.

Key
VII · 01

Codeforces

free

Multiple rated rounds weekly. Explicit AI-use restrictions during main contests.

codeforces.com
VII · 02

AtCoder

free

ABC/ARC/AGC/AHC lineups. Strict AI rules on ARC/AGC.

atcoder.jp
VII · 03

CodeChef

freemium

Core contests free. Pivoted heavily toward student placement prep.

codechef.com
VII · 04

Kaggle competitions

free

More active than ever in 2026. Free with GPU/TPU notebook quotas.

kaggle.com/competitions
VII · 05

Project Euler

free

Removed leaderboard due to cheating, adding rolling rank table. Free.

projecteuler.net
VII · 06

Advent of Code

free

Scaled to 12 puzzles + no global leaderboard in 2025 due to AI solvers and DDoS. Private leaderboards still work. Free.

adventofcode.com
VII · 07

CSES Problem Set

free

Not a contest platform — the algorithm learning problem set. No ads, no card.

cses.fi
VII · 08

TopCoder

free

Under Wipro. Pivoting to AI challenges vs classic SRMs. Community thinner than peak years.

topcoder.com
VII · 09

HackerEarth

freemium

Firmly pivoted to B2B hiring/assessment. HourStorm + monthly circuits still free.

hackerearth.com
VII · 10

SPOJ

free

Maintenance mode — no major new contests since 2022. Still a valuable practice archive.

spoj.com