VC中自行构建Stack（堆栈）类

template<class T>
class Stack{
struct Link{
   T* data;
   Link* next;
   Link(T* dat,Link* nxt):data(dat),next(nxt){}
   }*head;
public:
   Stack():head(0){}
   ~Stack(){
    while(head)
     delete pop();
   }
   void push(T* dat)
   {
    head=new Link(dat,head);
   }
   T* peek() const{
    return head?head->data:0;
   }
   T* pop(){
    if(head==0) return 0;
    T* result=head->data;
    Link* oldHead=head;
    head=head->next;
    delete oldHead;
    return result;
   }
};