Knight Dialer: Count Dialable Digit Sequences
Company: Whatnot
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Technical Screen
Overview: This question evaluates a candidate's ability to model constrained state transitions with dynamic programming, using a knight's legal moves on a phone keypad as the domain. It tests recognition that counting sequences under fixed transition rules reduces to tracking per-digit counts over discrete steps, a common way to probe DP-over-graph thinking in coding interviews. The problem sits at a practical application level, requiring an efficient algorithm rather than brute-force path enumeration.