ParkingSystem.java

// Source : https://leetcode.com/problems/design-parking-system/
// Author : zhoutianbin
// Date   : 2021-03-19

/***************************************************************************************************** 
 *
 * 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.
 *
 * Example 1:
 *
 * Input
 * ["ParkingSystem", "addCar", "addCar", "addCar", "addCar"]
 * [[1, 1, 0], [1], [2], [3], [1]]
 * Output
 * [null, true, true, false, false]
 *
 * Explanation
 * ParkingSystem parkingSystem = new ParkingSystem(1, 1, 0);
 * parkingSystem.addCar(1); // return true because there is 1 available slot for a big car
 * parkingSystem.addCar(2); // return true because there is 1 available slot for a medium car
 * parkingSystem.addCar(3); // return false because there is no available slot for a small car
 * parkingSystem.addCar(1); // return false because there is no available slot for a big car. It is 
 * already occupied.
 *
 * Constraints:
 *
 * 	0 <= big, medium, small <= 1000
 * 	carType is 1, 2, or 3
 * 	At most 1000 calls will be made to addCar
 ******************************************************************************************************/

package DesignParkingSystem;

public class ParkingSystem {
    // 只需要这三个变量就可以了，这是最简单的
    private int bigSlotLimit;
    private int meduimSlotLimit;
    private int smallSlotLimit;

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

    public boolean addCar(int carType) {
        switch (carType) {
            case 1:
                if (bigSlotLimit == 0) {
                    return false;
                } else {
                    bigSlotLimit--;
                }
                break;
            case 2:
                if (meduimSlotLimit == 0) {
                    return false;
                } else {
                    meduimSlotLimit--;
                }
                break;
            case 3:
                if (smallSlotLimit == 0) {
                    return false;
                } else {
                    smallSlotLimit--;
                }
                break;
            default:
                throw new IllegalArgumentException("Error cartype");
        }
        return true;
    }

    public  boolean addCar0(int carType) {
        if (carType == 1 && bigSlotLimit > 0) {
            bigSlotLimit--;
            return true;
        } else if (carType == 2 && meduimSlotLimit > 0) {
            meduimSlotLimit--;
            return true;
        } else if (carType == 3 && smallSlotLimit > 0) {
            smallSlotLimit--;
            return true;
        }
        return false;
    }

}