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Bloomberg·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Bloomberg coding round, one problem the whole session. Grid traversal with fuel constraints. Not the hardest thing I've done but I fumbled the state tracking part longer than I'd like to admit.

Questions Asked (1)

Q1

You're given a 2D grid with passable cells, obstacles, gas stations, a start, and an end. You begin with a fixed amount of fuel and spend 1 unit per move. Gas stations refill you to full. Can you reach the end?

Algorithms & Data Structures
Author's notes

My first instinct was plain BFS and I coded like half of it before realizing revisiting cells is actually valid here because your fuel level changes after hitting a gas station.

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AI HintsAI Generated

Suggested Approach

Model the problem as a graph where each cell is a node, and edges represent moves that consume fuel. Use BFS with state (row, col, fuel) to find the shortest path to the end, where fuel is capped at the tank capacity and refilled at gas stations. If the end is reachable, return true; otherwise, false.

Pro tip: Mention that you can optimize by treating fuel as a resource and using a priority queue to always expand the state with the most fuel, or by precomputing distances to nearest gas stations to prune the search space.

1. Clarify problem constraints

Ask about grid size, fuel capacity, number of gas stations, and whether moving through gas stations without refueling is allowed. Confirm if diagonal moves are permitted.

2. Define state representation

Represent each state as (row, column, current fuel). Since fuel can be up to the tank capacity, use a 3D visited array or a set to track visited states.

3. Choose search algorithm

Use BFS to explore states level by level, ensuring the shortest path in terms of moves. Alternatively, use Dijkstra if edge weights vary, but here all moves cost 1 fuel.

4. Handle refueling and boundaries

When moving to a gas station, set fuel to full capacity. Ensure fuel never goes negative and stays within bounds. Check for reaching the end cell.

5. Analyze complexity and optimize

Time complexity is O(R*C*F) where F is fuel capacity. Discuss possible optimizations like bidirectional BFS or A* with a heuristic based on Manhattan distance to the end.

Key Points to Mention

  • State space includes fuel level, so visited must track (row, col, fuel) to avoid cycles.
  • BFS guarantees shortest path in terms of moves, but if only reachability is needed, DFS with memoization also works.
  • Gas stations refill to full, so arriving with any fuel level resets to full; this can be modeled as a special transition.
  • Fuel capacity bounds the state space; if fuel capacity is large, consider alternative approaches like precomputing reachable regions.
  • Edge cases: start or end on obstacle, no gas stations, fuel insufficient to reach any gas station, end unreachable due to obstacles.
  • Optimization: use a priority queue to prioritize states with more fuel, or precompute distances to nearest gas station to guide search.

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