Parking System Design

Problem Description

Design a parking system for a parking lot. The parking lot has three kinds of parking spaces: big, medium, and small, with a fixed number of slots for each size.

Implement the ParkingSystem class:

• ParkingSystem(int big, int medium, int small) Initializes object of the ParkingSystem class. The number of slots for each parking space are given as part of the constructor.
• bool addCar(int carType) Checks whether there is a parking space of carType for the car that wants to get into the parking lot. carType can be of three kinds: big, medium, or small, which are represented by 1, 2, and 3 respectively. A car can only park in a parking space of its carType. If there is no space available, return false, else park the car in that size space and return true.

Naive Solution

A simple approach is to maintain separate counters for each parking space type (big, medium, small). The constructor initializes these counters with the given capacity. The addCar method checks if the counter for the given carType is greater than zero. If it is, decrement the counter and return true. Otherwise, return false.

Optimal Solution

The optimal solution is essentially the same as the naive solution since the problem constraints are simple and direct. We use the counters in the constructor and the addCar method.

Code Implementation (Java)

class ParkingSystem {
    private int big;
    private int medium;
    private int small;

    public ParkingSystem(int big, int medium, int small) {
        this.big = big;
        this.medium = medium;
        this.small = small;
    }

    public boolean addCar(int carType) {
        if (carType == 1) {
            if (big > 0) {
                big--;
                return true;
            } else {
                return false;
            }
        } else if (carType == 2) {
            if (medium > 0) {
                medium--;
                return true;
            } else {
                return false;
            }
        } else {
            if (small > 0) {
                small--;
                return true;
            } else {
                return false;
            }
        }
    }
}

Big O Analysis

• Time Complexity:
  • Constructor: O(1)
  • addCar: O(1)
• Space Complexity: O(1) - We use a fixed amount of space to store the counters, regardless of the input.

Edge Cases

• big, medium, or small can be 0. The code handles this correctly as the addCar method will return false if the corresponding counter is 0.
• Invalid carType values (e.g., less than 1 or greater than 3) are not explicitly handled in the provided code, but could be added via a conditional check that returns false. The problem states that carType will be 1, 2, or 3 so you would clarify this during the interview.