《Cracking the Coding Interview》——第8章：面向对象设计——题目4

2014-04-23 18:17

题目：设计一个停车位的类。

解法：停车位，就要有停车、取车的功能了。另外我还加了一个工作线程用于计费，每秒给那些有车的车位加1块钱费用。

代码：

// 8.4 Design a class to simulate the parking lot.
#include <iostream>
#include <string>
#include <thread>
#include <vector>
using namespace std;

class ParkingLot {
public:
    ParkingLot(int _capacity = 0):capacity(_capacity) {
        slots.resize(capacity);
        fees.resize(capacity);
        fill(slots.begin(), slots.end(), false);
        fill(fees.begin(), fees.end(), 0);
    };
    
    void start() {
        work = new thread(workThread, this);
    };
    
    void parkIn() {
        int i;
        
        for (i = 0; i < (int)slots.size(); ++i) {
            if (!slots[i]) {
                cout << "Car is parked at slot " << i << "." << endl;
                slots[i] = true;
                fees[i] = 1;
                return;
            }
        }
        
        cout << "Sorry, no more slot is available." << endl;
    };
    
    void getOut(int id) {
        if (id < 0 || id > (int)slots.size() - 1) {
            cout << "Invalid slot number." << endl;
            return;
        } else if (slots[id] == false) {
            cout << "The slot is empty." << endl;
            return;
        }
        
        cout << "Car in slot " << id << " is delivered. Total fee is " << fees[id] << " bucks." << endl;
        slots[id] = false;
        fees[id] = 0;
    };
    
    friend void workThread(ParkingLot *);
    
    ~ParkingLot() {
        slots.clear();
        fees.clear();
        work->detach();
        delete work;
    };
private:
    thread *work;
    int capacity;
    vector<bool> slots;
    vector<int> fees;
};

void workThread(ParkingLot *p)
{
    while (true) {
        // sleep for one second.
        _sleep(1000);
        for (int i = 0; i < p->capacity; ++i) {
            if (p->slots[i]) {
                ++p->fees[i];
            }
        }
    }
}

int main()
{
    ParkingLot *p;
    string cmd;
    int id;
    
    p = new ParkingLot(5);
    p->start();
    while (cin >> cmd) {
        if (cmd == "park") {
            p->parkIn();
        } else if (cmd == "get") {
            cin >> id;
            p->getOut(id);
        } else if (cmd == "end") {
            break;
        }
    }
    delete p;
    
    return 0;
}