How should I practice Closest Bathroom / Desk on a Grid?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Snowflake phone screen problems in FastPrep.

Is Closest Bathroom / Desk on a Grid associated with Snowflake?

FastPrep tags this as a Snowflake phone screen coding practice problem when the problem catalog has that company and stage context.

Problem

Closest Bathroom / Desk on a Grid

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Problem statement

You are given a two-dimensional office grid. Each cell contains one of three characters:

'B': a bathroom
'D': a desk
'_': an empty cell

Movement is allowed in the four cardinal directions, and the base version has no obstacles. For every desk cell, compute the shortest step distance to any bathroom.

Return an integer matrix with the same dimensions as grid. For cells containing desks, store the nearest-bathroom distance. For non-desk cells, store -1. If the grid has no bathrooms, every desk distance should be -1.

Function

closestBathroomDistances(grid: String[][]) → int[][]

Examples

Example 1

grid = [["B", "_", "D"], ["_", "D", "_"], ["D", "_", "B"]]return = [[-1, -1, 2], [-1, 2, -1], [2, -1, -1]]

Each desk is two steps away from the nearest bathroom using 4-directional movement.

Example 2

grid = [["D", "_"], ["_", "D"]]return = [[-1, -1], [-1, -1]]

There are no bathrooms in the grid, so no desk has a reachable bathroom.

Constraints

grid is a rectangular matrix.
Each cell is one of "B", "D", or "_".
Movement uses four directions: up, down, left, and right.