The core knowledge behind every LeetCode problem — distilled into 7 tiers, 15 recurring patterns, and a 234-problem practice plan. With diagrams, explanations, external resources, a constraints→complexity cheat sheet, a persistent progress tracker, and an AI tutor that knows where you are.
Read the constraints first — they tell you the required time complexity. Enter an n and the table highlights which algorithms are viable. This is the single most useful skill for picking an approach under pressure.
All 234 problems from the study plan. Cycle a problem's status with the dropdown — your progress saves to the server (no login, just an anonymous device id). Filter by phase, difficulty, or status; search by name or number.