01
Which pattern do I use?
Read the signal in a problem, then reach for the technique. Tap any row to filter the topics below.
02
Which data structure?
Patterns give you the plan; structures are the tools. Pick what you need to be fast and the matching structures light up.
Composite structures - some problems need two working together: LRU cache = hash map + doubly linked list · streaming median = two heaps · Dijkstra = graph + min-heap · sliding-window max = monotonic deque.
Read the full guide →
Read the full guide →
03
Browse every problem
Click a topic to expand its problems. Each links straight to the solution on GitHub. Difficulty is color-coded: easy, medium, hard. IMP marks priority problems.