C++primer Queue模板的构建

  1 #include<iostream>
  2 #include<vector>
  3 #include<string>
  4 using namespace std;
  5 
  6 
  7 template<class Type> class Queue;
  8 
  9 
 10 template <class T>
 11 ostream & operator<<(ostream&,const Queue<T>&);
 12 
 13 template <class Type> class QueueItem
 14 {
 15     friend class Queue<Type>;
 16     friend ostream&
 17         operator << <Type>(ostream&,const Queue<Type>& );
 18     QueueItem(const Type &t):item(t),next(0){}
 19     Type item;
 20     QueueItem *next;
 21 
 22 };
 23 
 24 template <class Type> class Queue
 25 {
 26     friend ostream&
 27         operator << <Type>(ostream&,const Queue<Type>& );
 28 public:
 29     Queue():head(0),tail(0){}
 30     template <class It>
 31     Queue(It beg,It end):
 32         head(0),tail(0){copy_elems(beg,end);}
 33     Queue(const Queue &Q):head(0),tail(0)
 34                         {copy_elems(Q);}
 35     ~Queue(){destroy();}
 36     template <class Iter> void assign(Iter,Iter);
 37     Type& front(){return head->item;}
 38     const Type &front() const {return head->item;}
 39     void push(const Type &);
 40     void pop();
 41     bool empty() const{
 42         return head==0;    }
 43 
 44 private:
 45     QueueItem<Type> *head;
 46     QueueItem<Type> *tail;
 47     void destroy();
 48     void copy_elems(const Queue&);
 49     template <class Iter> void copy_elems(Iter,Iter);
 50 
 51 
 52 };
 53 
 54 template <class Type> void Queue<Type>::destroy()
 55 {
 56     while(!empty())
 57         pop();
 58 
 59 }
 60 template <class Type> void Queue<Type>::pop()
 61 {
 62     QueueItem<Type> *p=head;
 63     head=head->next;
 64     delete p;
 65 
 66 }
 67 
 68 template <class Type> void Queue<Type>::push(const Type &val)
 69 {
 70     QueueItem<Type> *pt=new QueueItem<Type>(val);
 71     if(empty())
 72         head=tail=pt;
 73     else{
 74         tail->next=pt;
 75         tail=pt;
 76     }
 77 
 78 
 79 }
 80 
 81 template <class Type>
 82 void Queue<Type>::copy_elems(const Queue &orig)
 83 {    for(QueueItem<Type> *pt=orig.head;pt;pt=pt->next)
 84     push(pt->item);
 85 
 86 }
 87 
 88 template<class T> template <class Iter>
 89 void Queue<T>::assign(Iter beg,Iter end)
 90 {
 91     destroy();
 92     copy_elems(beg,end);
 93 }
 94 
 95 template<class Type> template <class It>
 96 void Queue<Type>::copy_elems(It beg,It end )
 97 {
 98     while(beg!=end)
 99     {
100         push(*beg);
101         ++beg;
102     }
103 
104 }
105 template<class Type>
106 ostream& operator <<(ostream &os,const Queue<Type> &q)
107 {
108     os<<"<";
109     QueueItem<Type>*p;
110     for(p=q.head;p;p=p->next)
111         os<<p->item<<" ";
112     os<<">";
113     return os;
114 
115 }
116 
117 
118 int main()
119 {
120     vector<int> iter;
121     iter.push_back(1);
122     iter.push_back(2);
123     iter.push_back(3);
124     iter.push_back(5);
125     cout<<" vector<int> test"<<endl;
126     Queue<int> qi(iter.begin(),iter.end());
127     //cout<<qi.front()<<endl;
128     cout<<qi<<endl;
129 
130     cout<<"vector<string> text"<<endl;
131     vector<string> ster;
132     ster.push_back("my");
133     ster.push_back("first");
134     ster.push_back("program");
135     ster.push_back("!");
136     Queue<string> qs(ster.begin(),ster.end());
137     //cout<<qs.front()<<endl;
138     cout<<qs<<endl;
139 
140 
141 
142 
143     cout<<"assign test"<<endl;
144     qi.assign(iter.begin(),iter.end()-1);
145     cout<<qi<<endl;
146 
147     
148 
149 
150 
151 
152 
153     return 0;
154 }