Leetcode is fine: lots of supported languages, large community, lots of solutions and editorials. Here are some more resources: - USACO: https://train.usaco.o

Leetcode is fine: lots of supported languages, large community, lots of solutions and editorials. Here are some more resources: - USACO: https://train.usaco.org/ https://train.usaco.org/ and https://usaco.guide/general/ https://usaco.guide/general/ - Codeforces: https://codeforces.com/ https://codeforces.com/ the de facto standard community for competitive programmers, regular contests with editorials, huge archive of problems (https://codeforces.com/problemset 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 https://codeforces.com/edu/courses that covers basic algorithms with practice problems.