Unisex Bathroom Problem

A bathroom is being designed for the use of both males and females in an office but requires the following constraints to be maintained:

• There cannot be men and women in the bathroom at the same time.
• There should never be more than three employees in the bathroom simultaneously.

The solution should avoid deadlocks. For now, though, don’t worry about starvation.

First let us come up with the skeleton of our Unisex Bathroom class. We want to model the problem programmatically first. We'll need two APIs, one that is called by a male to use the bathroom and another that is called by a female to use the bathroom. Initially, our class looks like the following:

class UnisexBathroomProblem:

    def __init__(self):
        pass

    def male_use_bathroom(self, name):
        pass

    def female_use_bathroom(self, name):
        pass

Let us try to address the first problem of allowing either men or women to use the bathroom. We'll worry about the max employees later. We need to maintain state in a variable to track which gender is currently using the bathroom. Let's call this variable in_use_by. The variable in_use_by will take on the values female, male or none to denote the gender currently using the bathroom.

We'll also have a method use_bathroom() that'll mock a person using the bathroom. The implementation of this method will simply sleep the thread using the bathroom for some time.

Assume there's no one in the bathroom and a male thread invokes the male_use_bathroom() ...