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Maven Clinic·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Got a graph problem at Maven Clinic for a software engineer role. One question, but it had enough layers to keep me busy for the whole session.

Questions Asked (1)

Q1

You're given a list of directed currency exchange rates (e.g. CAD to USD = 0.88, USD to JPY = 110). Given a source currency, a target currency, and an amount, return the converted amount rounded to 3 decimal places. Use the shortest path in terms of number of hops, and return None if no path exists.

Algorithms & Data StructuresTechnical Trade-offsSystem Design
Author's notes

I recognized the graph angle pretty fast, currencies as nodes and rates as weighted directed edges.

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AI HintsAI Generated

Suggested Approach

Model the currency exchange rates as a directed graph where currencies are nodes and rates are edges. Use BFS to find the shortest path in terms of number of hops from source to target, then multiply the rates along that path and round to 3 decimal places. If no path exists, return None.

Pro tip: Clarify edge cases upfront: what if source equals target (return amount as is), what if rates are given as strings, and whether the graph is guaranteed to be connected. Also, mention that BFS guarantees the shortest path in an unweighted graph, which is crucial here.

1. Clarify requirements and edge cases

Ask about input format (e.g., list of tuples, adjacency list), whether rates are floats or strings, and how to handle missing paths or same currency. Confirm rounding rules (e.g., standard rounding vs. banker's rounding).

2. Model as a graph

Represent currencies as nodes and exchange rates as directed edges with weights (the rates). Build an adjacency list for efficient traversal.

3. Find shortest path using BFS

Perform BFS from the source currency to find the target. Track the path or the cumulative product of rates. BFS ensures the path with the fewest hops.

4. Compute and round the result

Multiply the rates along the found path by the amount, then round to 3 decimal places. If no path is found, return None.

5. Analyze complexity and trade-offs

Discuss time and space complexity (O(V+E) for BFS). Mention alternative approaches like Dijkstra's algorithm if rates were considered as weights, but note that BFS is optimal for unweighted hop count.

Key Points to Mention

  • Graph representation: adjacency list for directed edges.
  • BFS guarantees shortest path in terms of number of hops.
  • Handling of edge cases: source == target, no path, invalid inputs.
  • Rounding to 3 decimal places: use round() or format, be aware of floating-point precision.
  • Time and space complexity: O(V+E) for BFS, O(V) space.
  • Potential follow-up: if rates are not commutative, ensure direction is respected.

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