用来两个栈实现一个队列。

题目：用来两个栈实现一个队列。



#include<stack>
template < class T>
class CQueue
{
public:
          

           void AppendTail(const T& Node)
          {
                   _s1.push( Node);
          }

           void DeleteHead()
          {
                    //如果_s2空，就把所有数据都倒入s2中
                    if (_s2.empty())
                   {
                              while (!_s1.empty())
                             {
                                      _s2.push(_s1.top());
                                      _s1.pop();
                             }
                             _s2.pop();
                   }
                    else //不为空，就先pop出去。
                   {
                             _s2.pop();
                   }

          }
          
           void Print()    //打印队列元素，分四种情况。
          {
                    if (_s1.empty() && _s2.empty())
                   {
                             cout << "The Queue is Empty!";
                   }
                   
                    else if (!_s1.empty() && _s2.empty())
                   {
                              while (!_s1.empty())
                             {
                                      _s2.push(_s1.top());
                                      _s1.pop();
                             }
                   
                              while (!_s2.empty())
                             {
                                      cout << _s2.top() << "  " ;
                                      _s2.pop();
                             }
                   }
                   
                    else if (_s1.empty() && !_s2.empty())
                   {
                              while (!_s2.empty())
                             {
                                      cout << _s2.top() << "  " ;
                                      _s2.pop();
                             }
                   }
                   
                    else
                   {
                              while (!_s2.empty())
                             {
                                      cout << _s2.top() << "  " ;
                                      _s2.pop();
                             }
                   
                              while (!_s1.empty())
                             {
                                      _s2.push(_s1.top());
                                      _s1.pop();
                             }
                   
                              while (!_s2.empty())
                             {
                                      cout << _s2.top() << "  " ;
                                      _s2.pop();
                             }
                   }
                   cout << endl;
          }
private:
           stack<T >  _s1;
           stack<T >  _s2;
};


void Test()
{
           CQueue<int > cq;
          cq.AppendTail(1);
          cq.AppendTail(2);
          cq.AppendTail(3);
          cq.AppendTail(4);
          cq.DeleteHead();
          cq.Print();
}

#include<stack>
template<class T>
class CQueue
{
public:
  
  void appendTail(const T& node)
  {
    stack1.push(node);
  }
  T deleteHead()
  {
    if (stack2.size() <= 0)
    {
      while (stack1.size() > 0)
      {
        T& data = stack1.top();
        stack1.pop();
        stack2.push(data);
      }
    }
    if (stack2.size() == 0)
      throw new exception("queue is empty");
      
    T head = stack2.top();
    stack2.pop();
    return head;
  }

private:
  stack<T> stack1;
  stack<T> stack2;
};