Queue.h

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 1 const int maxqueue = 50;
 2 
 3 enum Error_code
 4 {
 5     success, overflow, underflow, fail  //沒有;
 6 };
 7 
 8 template<class T>
 9 class Queue
10 {
11 public:
12     Queue();
13     bool empty() const;
14     Error_code serve();
15     Error_code append(const T &item);
16     Error_code retrieve(T &item) const;
17 protected:
18     int count;
19     int front, rear;
20     T entry[maxqueue];
21 };
22 
23 template <class T>
24 Queue<T>::Queue()
25 {
26     count = 0;
27     rear = maxqueue - 1;
28     front = 0;
29 }
30 
31 template <class T>
32 bool Queue<T>::empty() const
33 {
34     return count == 0;
35 }
36 
37 template <class T>
38 Error_code Queue<T>::append(const T &item)
39 {
40     if (count >= maxqueue)
41         return overflow;
42     count++;
43     rear = ((rear+1) == maxqueue) ? 0:(rear+1);
44     entry[rear] = item;
45     return success;
46 }
47 
48 template <class T>
49 Error_code Queue<T>::serve()
50 {
51     if (count <= 0)
52         return underflow;
53     count--;
54     front = ((front+1) == maxqueue) ? 0:(front+1);
55     return success;
56 }
57 
58 template <class T>
59 Error_code Queue<T>::retrieve(T &item) const
60 {
61     if (count <= 0)
62         return underflow;
63     item = entry[front];
64     return success;
65 }