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NURO·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Nuro SWE interview had a Minesweeper reveal problem that looked straightforward until I actually had to think through all the edge cases in the BFS expansion. Not a bad problem, just one where the details bite you if you're moving fast.

Questions Asked (1)

Q1

Implement the reveal logic for a Minesweeper board. Given a grid where cells can be unrevealed mines, unrevealed empty cells, or various revealed states, and a click coordinate, return the updated board following the standard rules: clicking a mine reveals it as exploded, clicking an empty cell with no adjacent mines triggers a flood-fill expansion in all 8 directions, and clicking an empty cell with adjacent mines just shows the count.

Algorithms & Data Structures
Author's notes

The BFS expansion part is where I slowed down.

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AI HintsAI Generated

Suggested Approach

Clarify the board representation and rules, then outline a solution using BFS/DFS for flood-fill. Emphasize edge cases like clicking a mine, already revealed cells, and boundary conditions, and discuss complexity.

Pro tip: Mention that you would use an iterative BFS with a queue to avoid recursion depth issues on large boards, and that you can optimize by only enqueuing cells that are empty with zero adjacent mines.

1. Clarify the problem

Ask about board representation (e.g., 'M' for mine, 'E' for empty, 'B' for blank, digits for counts, 'X' for exploded mine) and confirm the rules for flood-fill and mine reveal.

2. Handle immediate cases

If the clicked cell is a mine, change it to 'X' and return. If it's already revealed (not 'E'), return unchanged.

3. Compute adjacent mines

For the clicked empty cell, count mines in all 8 neighboring cells. If count > 0, update cell to the count and return.

4. Flood-fill expansion

If count == 0, set cell to 'B' and use BFS/DFS to reveal all connected empty cells with zero adjacent mines, stopping at cells with adjacent mines (revealing their counts).

5. Analyze complexity

Discuss time and space complexity: O(M*N) worst-case, and mention iterative BFS to avoid recursion limits.

Key Points to Mention

  • Board representation and cell states (e.g., 'E', 'M', 'B', digits, 'X')
  • Edge cases: clicking a mine, already revealed cell, out-of-bounds neighbors
  • Flood-fill algorithm (BFS/DFS) and stopping condition (cells with adjacent mines)
  • Direction vectors for 8 neighbors
  • Time and space complexity analysis
  • Iterative vs recursive implementation trade-offs

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.