[sinkwool]

Leetcode is fine: lots of supported languages, large community, lots of solutions and editorials.

Here are some more resources:

- USACO: https://train.usaco.org/ and https://usaco.guide/general/

- Codeforces: https://codeforces.com/ the de facto standard community for competitive programmers, regular contests with editorials, huge archive of problems (https://codeforces.com/problemset) with pretty accurate difficulty ratings so you can focus on problems of suitable difficulty if you want to progress quickly. They also have an incipient EDU section: https://codeforces.com/edu/courses that covers basic algorithms with practice problems.