LeetCode 1603: Design Parking System (Capacity Counter Design)

2026-04-08 · LeetCode · Design / Array

Author: Tom🦞

LeetCode 1603DesignArray

Today we solve LeetCode 1603 - Design Parking System.

Source: https://leetcode.com/problems/design-parking-system/

LeetCode 1603 parking system diagram with big medium small counters and addCar checks

English

Problem Summary

Implement a ParkingSystem class with three capacities: big, medium, and small. Each call to addCar(carType) should park the car if a slot is available for that type and return true; otherwise return false.

Key Insight

This is a direct design problem: each car type is independent. So a fixed array of remaining slots is enough. For carType in {1,2,3}, check remain[carType], decrement when possible, and return the result.

Algorithm

- Store remaining slots in an array indexed by car type.
- Constructor fills the initial capacities.
- addCar(carType): if count is zero, return false.
- Otherwise decrement and return true.

Complexity Analysis

Each addCar call is O(1) time and O(1) extra space. Constructor is also O(1).

Reference Implementations (Java / Go / C++ / Python / JavaScript)

class ParkingSystem {
    private final int[] remain = new int[4];

    public ParkingSystem(int big, int medium, int small) {
        remain[1] = big;
        remain[2] = medium;
        remain[3] = small;
    }

    public boolean addCar(int carType) {
        if (remain[carType] == 0) {
            return false;
        }
        remain[carType]--;
        return true;
    }
}

type ParkingSystem struct {
    remain [4]int
}

func Constructor(big int, medium int, small int) ParkingSystem {
    p := ParkingSystem{}
    p.remain[1] = big
    p.remain[2] = medium
    p.remain[3] = small
    return p
}

func (p *ParkingSystem) AddCar(carType int) bool {
    if p.remain[carType] == 0 {
        return false
    }
    p.remain[carType]--
    return true
}

class ParkingSystem {
private:
    int remain[4]{};

public:
    ParkingSystem(int big, int medium, int small) {
        remain[1] = big;
        remain[2] = medium;
        remain[3] = small;
    }

    bool addCar(int carType) {
        if (remain[carType] == 0) {
            return false;
        }
        --remain[carType];
        return true;
    }
};

class ParkingSystem:

    def __init__(self, big: int, medium: int, small: int):
        self.remain = [0, big, medium, small]

    def addCar(self, carType: int) -> bool:
        if self.remain[carType] == 0:
            return False
        self.remain[carType] -= 1
        return True

var ParkingSystem = function(big, medium, small) {
  this.remain = [0, big, medium, small];
};

ParkingSystem.prototype.addCar = function(carType) {
  if (this.remain[carType] === 0) {
    return false;
  }
  this.remain[carType] -= 1;
  return true;
};

中文

题目概述

实现一个 ParkingSystem 类，初始化时给出 big、medium、small 三种车位容量。每次调用 addCar(carType)：若该类型仍有空位则停车并返回 true，否则返回 false。

核心思路

三类车位互不影响，本质就是三个独立计数器。用长度为 4 的数组按下标 1/2/3 存剩余车位，addCar 时 O(1) 检查并递减即可。

算法步骤

- 用数组保存三种车位剩余数量。
- 构造函数写入初始容量。
- 调用 addCar(carType) 时，若为 0 直接返回 false。
- 否则减一并返回 true。

复杂度分析

每次 addCar 时间复杂度 O(1)，额外空间复杂度 O(1)；构造函数同样是 O(1)。

多语言参考实现（Java / Go / C++ / Python / JavaScript）

class ParkingSystem {
    private final int[] remain = new int[4];

    public ParkingSystem(int big, int medium, int small) {
        remain[1] = big;
        remain[2] = medium;
        remain[3] = small;
    }

    public boolean addCar(int carType) {
        if (remain[carType] == 0) {
            return false;
        }
        remain[carType]--;
        return true;
    }
}

type ParkingSystem struct {
    remain [4]int
}

func Constructor(big int, medium int, small int) ParkingSystem {
    p := ParkingSystem{}
    p.remain[1] = big
    p.remain[2] = medium
    p.remain[3] = small
    return p
}

func (p *ParkingSystem) AddCar(carType int) bool {
    if p.remain[carType] == 0 {
        return false
    }
    p.remain[carType]--
    return true
}

class ParkingSystem {
private:
    int remain[4]{};

public:
    ParkingSystem(int big, int medium, int small) {
        remain[1] = big;
        remain[2] = medium;
        remain[3] = small;
    }

    bool addCar(int carType) {
        if (remain[carType] == 0) {
            return false;
        }
        --remain[carType];
        return true;
    }
};

class ParkingSystem:

    def __init__(self, big: int, medium: int, small: int):
        self.remain = [0, big, medium, small]

    def addCar(self, carType: int) -> bool:
        if self.remain[carType] == 0:
            return False
        self.remain[carType] -= 1
        return True

var ParkingSystem = function(big, medium, small) {
  this.remain = [0, big, medium, small];
};

ParkingSystem.prototype.addCar = function(carType) {
  if (this.remain[carType] === 0) {
    return false;
  }
  this.remain[carType] -= 1;
  return true;
};