Bloomberg·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Bloomberg SWE interview with an interactive coding problem that punishes brute force pretty hard. The API call limit forces you toward a smarter approach, which was a nice change from the usual grind-it-out problems.

Questions Asked (1)

Given a rectangle defined by its top-right and bottom-left corners, count the number of ships inside it. You can only query a helper function that returns true if at least one ship exists in a given sub-rectangle. There are at most 10 ships total, and you're limited to 400 calls.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

The call limit is what makes this interesting.

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AI HintsAI Generated

Suggested Approach

Use a divide-and-conquer strategy: recursively split the rectangle into sub-rectangles and query each to determine if it contains any ships. Since there are at most 10 ships, you can prune empty regions early and stop when you've found all ships or when sub-rectangles are small enough to count directly. Aim to minimize the number of queries by splitting efficiently and leveraging the sparsity of ships.

Pro tip: Mention that the worst-case number of queries is bounded by O(k log(Area)) where k is the number of ships, and that you can optimize by splitting along the longer dimension to reduce depth. Also, note that you can stop early once you've found all 10 ships, which often happens before exploring the entire space.

1. Clarify the problem and constraints

Confirm the rectangle boundaries, the helper function's behavior, and that ships are points or small rectangles. Ask about the maximum number of ships (10) and query limit (400) to ensure you understand the scale.

2. Design a recursive divide-and-conquer algorithm

Split the current rectangle into two halves (e.g., along the longer side). Query each half; if a half returns false, discard it. If true, recurse on that half until the sub-rectangle is small enough to contain at most one ship.

3. Handle base cases and count ships

When a sub-rectangle is reduced to a single cell (or minimal size), query it to confirm a ship and increment the count. Alternatively, if a sub-rectangle is known to contain exactly one ship (e.g., by binary search), count it without further splitting.

4. Optimize query usage and early termination

Keep track of the number of ships found; stop when you reach 10. Choose split dimensions to minimize depth, and avoid redundant queries by caching results or using binary search to locate ships precisely.

5. Analyze complexity and edge cases

Discuss the worst-case query count (e.g., O(k log(Area))) and verify it stays under 400. Consider edge cases: no ships, all ships in one corner, ships on boundaries, and the helper function's behavior for empty rectangles.

Key Points to Mention

Divide-and-conquer approach with pruning empty regions
Binary search to isolate individual ships within a sub-rectangle
Early termination once all ships are found
Query complexity analysis: O(k log(Area)) with k ≤ 10
Choosing split direction (longer dimension) to reduce recursion depth
Handling edge cases: empty rectangle, ships on boundaries, and maximum ship count

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