offer_9

//面试题9:用两个栈实现队列
template<typename T> void CQueue<T>::appendTail(const T& element)
{
  stack1.push(element);
}

template<typename T>
T CQueue<T>::deleteHead()
{
  if(stack2.size()<=0){
    while(stack1.size()>0){
      T& data=stack1.top;
      stack1.pop();
      stack2.push(data);
     }
  }
  
  if(stack.size()==0)
    throw new exception("queue is empty"); 
  T head=stack2.top();
  stack2.pop();
  return head;
  
}