Pick a set. Every problem teaches the idea first with drawings, then lets you write and test code in your own language.

• Free50 problems

  Starter 50

  Fifty classic problems that cover every pattern once. The place to begin.

  Open

• Free75 problems

  Classic 75

  A widely shared list of 75 problems, in our learning order and our own wording.

  Open

• Pro75 problems

  Most-Asked 75

  The coding problems candidates report most often across top tech companies, ranked by how widely they appear. Every problem teaches the idea first.

  Open

• Pro34 problems

  AI Company Interviews

  Practical, staged problems reported at AI labs and high-growth startups. Explanation comes first: understand the problem, build the idea, then solve it.

  Open

Prefer to learn by idea? Browse by pattern.