Learning
Practice, Mocks & Interviews
Problem sets, contests and mock interviews, for keeping sharp or getting hired.
Where to start
For interviews, a curated list beaten thoroughly beats a thousand problems attempted once — NeetCode exists for exactly that reason. Contests are a different skill from interviews; do them because they are enjoyable, not because you think they are the same practice. System design is the part most people under-prepare and the part senior interviews turn on.
Interview preparation5
- NeetCodeCoreFree tier
A curated ordering of the problems that actually recur, with worked video solutions. The efficient path through LeetCode.
- LeetCodeCoreFree tier
The de facto interview problem set. Company-tagged questions and mock timers need a subscription.
- System Design PrimerAdvancedFree
The most complete free system design resource, with worked examples and flash cards.
- PrampCoreFree
Free peer-to-peer mock interviews. You interview someone, then they interview you.
- Tech Interview HandbookStart hereFree
The non-coding half nobody prepares: behavioural questions, resume, negotiation. Free and unusually specific.
Daily practice4
- HackerRankStart hereFree
Problems by domain plus skill certifications, and the platform many employers use for take-home screens.
- CodewarsStart hereFree
Small graded exercises where you can read everyone else’s solution afterwards, which is the useful part.
- Project EulerAdvancedFree
Mathematical problems where the naive solution will not finish. Teaches complexity better than any lecture.
- Advent of CodeStart hereFree
Twenty-five puzzles each December, every past year still playable. The friendliest way to learn a new language.
Contests3
- CodeforcesAdvancedFree
The main competitive programming site. Regular rated contests and an enormous archive.
- AtCoderCoreFree
Beginner contests with unusually clear problem statements and English editorials.
- Kaggle CompetitionsCoreFree
Machine learning contests with public leaderboards. The winning write-ups are the real teaching material.
About this list
12 resources, checked automatically every week so dead links do not sit here unnoticed. Nothing on this page is sponsored and none of these links pay us — which is the only reason a recommendation on it is worth anything. Every link goes to the original source, and we take nothing with you when you leave.