《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 <  || id > (int)songs.size() - ) {
             return;
         }
         song_list.push(id);
     }

     friend void workThread(JukeBox *);

     ~JukeBox() {
         while (!song_list.empty()) {
             song_list.pop();
         }
         size_t i;
         for (i = ; 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 = ; 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 = ; 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 ;
 }