How should I practice Nearest Charging Station on a Grid?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Spotify onsite interview problems in FastPrep.

Is Nearest Charging Station on a Grid associated with Spotify?

FastPrep tags this as a Spotify onsite interview coding practice problem when the problem catalog has that company and stage context.

Nearest Charging Station on a Grid

Spotify● MediumFULLTIMEONSITE INTERVIEW

Problem statement

Source note: The post says: "Given a 2-D grid with cells marked C (charging station), V (electric vehicle), and (empty), return the shortest distance from each vehicle to its nearest charging station under 4-directional movement." It also says there are no obstacles in the base case, and that empty grids and grids with no V cells are valid. The post gathers several reports, and its 1-D and assignment versions are separate problems here.

The post's symbol for an empty cell did not come through, so here it is a dot. The post does not give a return format or say what happens with no charger. Here, you return one distance for each vehicle, row by row and left to right, and -1 for every vehicle when the grid has no charger. Grids have at most 100 rows and 100 columns.

The judged task matches the post at about 90%.

You are given a grid as an array of strings. Each cell is one of:

C: a charging station
V: an electric vehicle
.: an empty cell

A vehicle moves one cell at a time, up, down, left or right. The grid has no obstacles, so a vehicle can pass through any cell, including other vehicles and charging stations.

For each vehicle, find the fewest moves it needs to reach any charging station. Return these distances in an array, going row by row from the top and left to right within each row. If the grid has no charging station, the distance for every vehicle is -1.

An empty grid or a grid with no vehicles returns an empty array.

Function

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

Examples

Example 1

grid = ["V.C","...","C.V"]return = [2,2]

The vehicle at row 0, column 0 is two moves from the station at row 0, column 2. The vehicle at row 2, column 2 is two moves from the station at row 0, column 2. The answer lists them in row order: [2,2].

Example 2

grid = ["C...V"]return = [4]

The only vehicle is at column 4 and the only station is at column 0, so it needs 4 moves.

Example 3

grid = ["V.V"]return = [-1,-1]

There is no charging station, so both vehicles get -1.

Example 4

grid = ["...","C.C"]return = []

There is no vehicle, so the answer is an empty array.

Constraints

0 <= grid.length <= 100
1 <= grid[i].length <= 100
All rows have the same length.
Every character of grid[i] is C, V or .