Design a Crossword Puzzle Solver

A crossword puzzle solver is a service that takes a puzzle board with empty word slots and a dictionary, then finds a valid assignment of words that satisfies all constraints. The core challenge is solving a constraint satisfaction problem (CSP) at scale—when brute force on a single machine won't finish in time.

This walkthrough follows the Interview Framework. Use it as a guide, not a script—adapt based on interviewer cues.