Unit 13 · Module 3 · Complexity and data structures
Graphs, BFS and DFS
Most "hard" interview problems are a graph you did not recognise.
Unit 13 of the free 49-unit computer-science course, in complexity and data structures. 1 topic to watch or read and a short self-check.
Watch or read
One topic makes up this unit. Take each one whichever way suits you, then answer the questions below.
Vector search with HNSW
HNSW turns nearest-neighbor search from brute-force (2M comparisons, 1.2s) into a hierarchical graph walk (1.8k comparisons, 2ms). Learn how greedy navigation trades exact answers for speed.
Self-check — 3 questions
Answer alone, at 2am, with no interviewer in the room.