《Cracking the Coding Interview》——第8章：面向对象设计——题目3

2014-04-23 18:10

题目：设计一个点唱机。

解法：英文叫Musical Jukebox。这是点唱机么？卡拉OK么？这种题目实在是云里雾里，又没有交流的余地，我索性用一个vector来表示一首曲子吧。不过有一点是肯定的，点播行为和播放行为应该分不同线程操作，这样就不至于让机器一直卡在那儿等你点歌了。

代码：

// 8.3 Design a data structure to simulate a musical jukebox.
#include <iostream>
#include <queue>
#include <string>
#include <thread>
#include <vector>
using namespace std;

class JukeBox {
public:
    JukeBox() {};
    
    void start() {
        work = new thread(workThread, this);
    };

    void addSong(vector<int> &song) {
        songs.push_back(song);
    }
    
    void orderSong(int id) {
        if (id < 0 || id > (int)songs.size() - 1) {
            return;
        }
        song_list.push(id);
    }

    friend void workThread(JukeBox *);

    ~JukeBox() {
        while (!song_list.empty()) {
            song_list.pop();
        }
        size_t i;
        for (i = 0; i < songs.size(); ++i) {
            songs[i].clear();
        }
        songs.clear();
        work->detach();
        delete work;
    };
private:
    queue<int> song_list;
    vector<vector<int> > songs;
    thread *work;
};

void workThread(JukeBox *jb) {
    size_t i;
    while (true) {
        if (!jb->song_list.empty()) {
            for (i = 0; i < jb->songs[jb->song_list.front()].size(); ++i) {
                cout << jb->songs[jb->song_list.front()][i] << ' ';
            }
            cout << endl;
            jb->song_list.pop();
        }
    }
};

int main()
{
    JukeBox *jb;
    string cmd;
    int id;
    int i, n;
    vector<int> song;

    jb = new JukeBox();
    jb->start();
    while (cin >> cmd) {
        if (cmd == "add") {
            cin >> n;
            song.resize(n);
            for (i = 0; i < n; ++i) {
                cin >> song[i];
            }
            jb->addSong(song);
        } else if (cmd == "order") {
            cin >> id;
            jb->orderSong(id);
        } else if (cmd == "end") {
            break;
        }
    }
    delete jb;

    return 0;
}