How should I practice Minimum Cleaning Robot Runs?

Start by reading the full statement, solve the visible examples, then compare the pattern against related HSBC online assessment problems in FastPrep.

Is Minimum Cleaning Robot Runs associated with HSBC?

FastPrep tags this as a HSBC online assessment coding practice problem when the problem catalog has that company and stage context.

Problem · Matrix

Minimum Cleaning Robot Runs

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● Medium

HSBCNEW GRADOA

Problem statement

A building plan is represented by a rectangular array of strings. Each field contains one of three symbols:

. is clean floor.
* is dirty floor.
# is a wall.

A room is a maximal group of non-wall fields connected in the four cardinal directions. In one run, a cleaning robot starts in one room and cleans every dirty field in that room. It cannot cross a wall or leave the plan.

Return the minimum number of robot runs needed to clean every dirty field.

Function

solution(plan: String[]) → int

Examples

Example 1

plan = ["..#..",".*#*.","..#.."]return = 2

The vertical wall separates the floor into two rooms. Each room contains a dirty field, so the robot needs one run in each room.

Example 2

plan = ["....",".##.",".*#.","...."]return = 1

All non-wall fields are connected around the wall block. The single dirty field is therefore cleaned in one run.

Example 3

plan = ["###","#.#","###"]return = 0

The only floor field is already clean, so no robot run is required.

Constraints

1 <= plan.length and every row has the same positive length.
plan.length * plan[0].length <= 200000.
Every character is ., *, or #.