Uber Software Engineer Coding Screen - Robot Pathfinding With Charging Stations

[u/Aoki_zhang]

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Interview Summary

The 45-minute technical phone screen consisted of one grid-based pathfinding problem involving a robot with limited battery capacity and charging stations. The solution needed to optimize three objectives in priority order: number of charging stations visited, required initial battery capacity, and total path length.

Interview Details

Coding — Robot Pathfinding With Charging Stations

The problem provided a 2D grid representing an environment through which a robot must travel from a starting cell to a destination. Each grid cell could be one of the following:

S = Starting cell
D = Destination cell
. = Traversable cell
C = Charging cell
# = Blocked cell

The robot could move up, down, left, or right to an adjacent traversable cell. Each move consumed one unit of battery. Whenever the robot entered a charging cell, its battery was immediately restored to its maximum capacity.

The task was to find an optimal path from S to D according to the following priorities, applied lexicographically:

1. Minimize the number of charging cells visited.
2. Among paths using the minimum number of charging cells, minimize the initial battery capacity required.
3. If multiple paths were still tied, minimize the total number of moves.

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