类模板Queue的实现

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  1 #include <iostream>  2 #include <vector>  3 using namespace std;  4   5 template <class Type> class Queue;  6 template <class T > ostream & operator << (ostream &os, const Queue<T> &);  7   8 template <class Type> class QueueItem {  9     friend class Queue<Type >; 10     friend ostream & operator << <Type> (ostream &os, const Queue<Type> &); 11     //private class 12     QueueItem(const Type &val) : Item(val), next(0) {} 13     Type Item; 14     QueueItem<Type > *next; 15 }; 16  17 template <class Type> class Queue { 18     friend ostream & operator << <Type> (ostream &os, const Queue<Type> &); 19  20 public: 21     Queue() : head(0), tail(0) {} 22     template <class It> Queue(It _beg, It _end) : head(0), tail(0) { copy_elems(_beg, _end); } 23     Queue(const Queue<Type> &Q) : head(0), tail(0) { copy_elems(Q); } 24     Queue& operator = (const Queue &Q); 25     ~Queue() { Destroy(); } 26     template <class Iter> void _assign(Iter, Iter); 27     Type &_front() { return head->Item; } 28     const Type &_front() const { return head->Item; } 29     void _push(const Type&); 30     void _pop(); 31     bool _empty() const { return head == 0; } 32  33 private: 34     QueueItem<Type> *head; 35     QueueItem<Type> *tail; 36     void Destroy(); 37     void copy_elems(const Queue<Type> &); 38     template <class Iter> void copy_elems(Iter, Iter); 39 }; 40  41 template <class Type> Queue<Type>& Queue<Type>::operator = (const Queue<Type> &q) 42 { 43     if (this != &q) { 44         head = tail = 0; 45         for (QueueItem<Type> *pt = q.head; pt; pt= pt->next) { 46             _push(pt->Item); 47         } 48     } 49     return *this; 50 } 51  52 template <class Type> void Queue<Type>::copy_elems(const Queue<Type> &q) 53 { 54     for (QueueItem<Type> *pt = q.head; pt; pt = pt->next) { 55         _push(pt->Item); 56     } 57 } 58 template <class Type> template <class Iter> void Queue<Type>::copy_elems(Iter _beg, Iter _end) 59 { 60     while (_beg != _end) { 61         _push(*_beg); 62         ++_beg; 63     } 64 } 65  66 template <class Type> template <class Iter> void Queue<Type>::_assign(Iter _beg, Iter _end) 67 { 68     head = tail = 0; 69     copy_elems(_beg, _end); 70 } 71  72 template <class Type> void Queue<Type>::_push(const Type& val) 73 { 74     QueueItem<Type> *p = new QueueItem<Type>(val); 75     if (_empty()) { 76         head = tail = p; 77     } else { 78         tail->next = p; 79         tail = p; 80     } 81 } 82  83 template <class Type> void Queue<Type>::_pop() 84 { 85     QueueItem<Type> *p = head; 86     head = head->next; 87     delete p; 88 } 89  90 template <class Type> ostream & operator << (ostream &os, const Queue<Type> &q) 91 { 92     for (QueueItem<Type> *pt = q.head; pt; pt = pt->next) { 93         os << pt->Item << " "; 94     } 95     os << endl; 96     return os; 97 } 98  99 template <class Type> void Queue<Type>::Destroy()100 {101     while (!_empty()) _pop();102 }103 104 105 int main()106 {107     Queue<int >que;108     que._push(1);109     que._push(2);110     que._push(3);111     que._push(4);112     cout << que;113     que._pop();114     cout << que;115     Queue<int >q2, q1(que);116     cout << q1;117     cout << q2._empty() << endl;118     q2 = q1;119     cout << q2;120     while (!que._empty()) {121         cout << que._front() << endl;122         que._pop();123     }124     vector<int > vet(10, 7);125     for (int i = 0; i < (int)vet.size(); i++) {126         cout << vet[i] << ' ';127     }128     cout << endl;129     que._assign(vet.begin(), vet.end());130     cout << que;131     return 0;132 }
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