The follow-up to number-of-islands, and the question where candidates reveal whether they understand WHY BFS finds shortest paths. Plus the two variants (weights, eliminating obstacles) that decide hard-screen outcomes at xAI.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
The follow-up to number-of-islands, and the question where candidates reveal whether they understand WHY BFS finds shortest paths. Plus the two variants (weights, eliminating obstacles) that decide hard-screen outcomes at xAI.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.