面試題6：用兩個棧實現隊列

思路：設置兩個棧stack1和stack2，stack1實現入隊列功能，stack2實現出隊列功能。

（1）入隊列：入棧stack1

（2）出隊列：若stack2不空，則直接彈出stack2中的棧頂元素

              若stack2為空，則依次彈出stack1中的元素放入stack2中，再彈出stack2中的棧頂元素

C++代碼：

#include "stdafx.h"   
#include <iostream>   
#include <stack>   
using namespace std;  
  
template<class T>  
class CQueue  
{  
public:  
    CQueue(void);  
    ~CQueue(void);  
    void AddTail(const T &addData);  
    void DeleteHead(T &deleteData);  
  
private:  
    stack<T> stack1;  
    stack<T> stack2;  
};  
  
template<class T>  
CQueue<T>::CQueue(void)  
{  
  
}  
  
template<class T>  
CQueue<T>::~CQueue(void)  
{  
  
}  
  
template<class T>  
void CQueue<T>::AddTail(const T &addData)  
{  
   stack1.push(addData);  
}  
  
template<class T>  
void CQueue<T>::DeleteHead(T &deleteData)  
{  
   if (stack2.empty())  
   {  
       while (!stack1.empty())  
       {  
           T topData = stack1.top();  
           stack2.push(topData);  
           stack1.pop();  
       }  
   }  
  
   if (stack2.empty())  
   {  
       cout << "隊列中無元素！" << endl;  
   }  
   else  
   {  
       deleteData = stack2.top();  
       stack2.pop();  
   }  
}  
  
int _tmain(int argc, _TCHAR* argv[])  
{  
    CQueue<int> q;  
    for (int i=0; i<6; i++)  
    {  
        q.AddTail(i);  
    }  
  
    int deleteData = 0;  
    for (int i=0; i<6; i++)  
    {         
        q.DeleteHead(deleteData);  
        cout << deleteData << " ";  
    }  
    cout << endl;  
  
    q.DeleteHead(deleteData);  
  
    system("pause");  
    return 0;  
}  
#include "stdafx.h"
#include <iostream>
#include <stack>
using namespace std;

template<class T>
class CQueue
{
public:
	CQueue(void);
	~CQueue(void);
	void AddTail(const T &addData);
	void DeleteHead(T &deleteData);

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

template<class T>
CQueue<T>::CQueue(void)
{

}

template<class T>
CQueue<T>::~CQueue(void)
{

}

template<class T>
void CQueue<T>::AddTail(const T &addData)
{
   stack1.push(addData);
}

template<class T>
void CQueue<T>::DeleteHead(T &deleteData)
{
   if (stack2.empty())
   {
	   while (!stack1.empty())
	   {
		   T topData = stack1.top();
		   stack2.push(topData);
		   stack1.pop();
	   }
   }

   if (stack2.empty())
   {
	   cout << "隊列中無元素！" << endl;
   }
   else
   {
	   deleteData = stack2.top();
	   stack2.pop();
   }
}

int _tmain(int argc, _TCHAR* argv[])
{
	CQueue<int> q;
	for (int i=0; i<6; i++)
	{
		q.AddTail(i);
	}

	int deleteData = 0;
	for (int i=0; i<6; i++)
	{		
		q.DeleteHead(deleteData);
		cout << deleteData << " ";
	}
	cout << endl;

	q.DeleteHead(deleteData);

	system("pause");
	return 0;
}