队列 讲义实现

顺序队列

基本操作和顺序链表和顺序栈差不多，注意其有两个指针，头尾指针
头出(删除元素)尾进(添加元素)

实现

#include <iostream>
using namespace std;

const int QUEUE_INIT_SIZE = 20;
const int OVERFLOW = 0;
const int ERROR = 0;
const int OK = 1;
const int EMPTY = 0;

typedef int Status;

template <class T>
class SqQueue
{
public:
	SqQueue();
	//~SqQueue();
	Status EnQueue(T e);
	Status DeQueue(T &e);
	int QueueLength() const;
	Status IsEmpty();
	void DispQueue();

private:
	T *base;	//内存空间首地址
	T *front;	//头指针
	T *rear;	//尾指针
	int queueSize;	//队列的长度
};

//初始化顺序队列
template <class T>
SqQueue<T>::SqQueue()
{
	base = new T[QUEUE_INIT_SIZE];
	if(!base)
	{
		cerr << "存储分配失败！"<<endl;
	}
	front = rear = base;		//注意此处的赋值顺序,将base赋值给front和rear
	queueSize = QUEUE_INIT_SIZE;
}

template <class T>
SqQueue<T>::~SqQueue()
{
	T *p = front;
	while(p != rear)
	{
		p++;
		delete front;
		front = p;
	}
}

//顺序入队
template <class T>
Status SqQueue<T>::EnQueue(T e)
{
	if(rear-base >= queueSize)
	{
		return ERROR;
	}
	*rear++ = e;	//先赋值，再加指针
	return OK;
}

//顺序队列出队
template <class T>
Status SqQueue<T>::DeQueue(T &e)
{
	if(rear == front)
	{
		return ERROR;
	}
	e = *front++;	//先减指针，再取值
	return OK;
}

template <class T>
int SqQueue<T>::QueueLength() const
{
	return (rear-front);
}

template <class T>
Status SqQueue<T>::IsEmpty()
{
	if(front == rear)
	{
		return EMPTY;
	}
	else
	{
		return !EMPTY;
	}
}


template <class T>
void SqQueue<T>::DispQueue()
{
	T *p = front;
	while(p != rear)
	{
		cout << *p << " ";
		p++;
	}
	cout<< endl;
}


int main()
{
	SqQueue<int> queue1;
	cout << "Enter a queue!~" <<endl;
	for(int i=0; i<10; i++)
	{
		queue1.EnQueue(i);
	}
	queue1.DispQueue();
	cout << "The length of the queue is " << queue1.QueueLength()<<endl;
	int temp = 0;
	cout << "The first five nodes are out of the queue, they are: ";
	for(int i=0; i<5; i++)
	{
		queue1.DeQueue(temp);
		cout << temp << " ";
	}
	cout << endl;
	cout << "The rest of the queue are: ";
	queue1.DispQueue();
	cout << "Now, the length of the queue is " <<queue1.QueueLength()<<endl;
	cout << "The queue is empty? "<<queue1.IsEmpty()<<endl;
	for(int i=0; i<5; i++)
	{
		queue1.DeQueue(temp);
		cout << temp << " ";
	}
	queue1.DispQueue();
	cout << "The queue is empty? " << queue1.IsEmpty()<<endl;
	return 0;
}

循环队列

#include <iostream>
using namespace std;

const int QUEUE_INIT_SIZE = 20;
const int OVERFLOW = 0;
const int ERROR = 0;
const int OK = 1;
const int EMPTY = 0;

typedef int Status;

template <class T>
class CircularQueue
{
public:
	CircularQueue();
	~CircularQueue();
	Status EnQueue(T e);
	Status DeQueue(T &e);
	int QueueLength() const;
	Status IsEmpty();
	void DispQueue();

private:
	T *base;	//内存空间首地址
	int front;	//头指针
	int rear;	//尾指针
	int queueSize;	//队列的长度
};

template <class T>
CircularQueue<T>::CircularQueue()
{
	base = new T[QUEUE_INIT_SIZE];
	if(!base)
	{
		cerr << "存储分配错误！~"<<endl;
	}
	front = rear = 0;
	queueSize = QUEUE_INIT_SIZE;
}

template <class T>
CircularQueue<T>::~CircularQueue()
{
	delete[] base;
}

template <class T>
int CircularQueue<T>::QueueLength() const
{
	//确保其为一个正数再取模
	return (rear-front+QUEUE_INIT_SIZE) % QUEUE_INIT_SIZE;
}

template <class T>
void CircularQueue<T>::DispQueue()
{
	int p = front;
	while(p != rear)
	{
		cout<< base[p] << " ";
		p = (p + 1) % QUEUE_INIT_SIZE;
	}
	cout << endl;
}

template <class T>
Status CircularQueue<T>::EnQueue(T e)
{
	if((rear+1)%QUEUE_INIT_SIZE == front)
	{
		return ERROR;
	}
	base[rear] = e;
	rear = (rear + 1) % QUEUE_INIT_SIZE;
	return OK;
}

template <class T>
Status CircularQueue<T>::DeQueue(T &e)
{
	if(rear == front)
	{
		return EMPTY;
	}
	e = base[front];
	front = (front + 1) % QUEUE_INIT_SIZE;
	return OK;
}

template <class T>
Status CircularQueue<T>::IsEmpty()
{
	return (rear == front)?EMPTY:!EMPTY;
}

int main()
{
	CircularQueue<int> queue1;
	cout << "Enter a queue!~" <<endl;
	for(int i=0; i<10; i++)
	{
		queue1.EnQueue(i);
	}
	queue1.DispQueue();
	cout << "The length of the queue is " << queue1.QueueLength()<<endl;
	int temp = 0;
	cout << "The first five nodes are out of the queue, they are: ";
	for(int i=0; i<5; i++)
	{
		queue1.DeQueue(temp);
		cout << temp << " ";
	}
	cout << endl;
	cout << "The rest of the queue are: ";
	queue1.DispQueue();
	cout << "Now, the length of the queue is " <<queue1.QueueLength()<<endl;
	cout << "The queue is empty? "<<queue1.IsEmpty()<<endl;
	for(int i=0; i<5; i++)
	{
		queue1.DeQueue(temp);
		cout << temp << " ";
	}
	queue1.DispQueue();
	cout << "The queue is empty? " << queue1.IsEmpty()<<endl;


	return 0;
}

注意 成员函数操作数据成员时一定要避免修改数据成员。。。

链队列

#include <iostream>
using namespace std;

const int OVERFLOW = 0;
const int ERROR = 0;
const int OK = 1;
const int EMPTY = 0;

typedef int Status;

template <class T>
struct Node
{
	T data;
	Node<T> *next;
};

template <class T>
class LinkQueue
{
public:
	LinkQueue();
	~LinkQueue();
	Status EnQueue(T e);
	Status DeQueue(T &e);
	int QueueLength();
	Status IsEmpty();
	void DispQueue();

private:
	Node<T> *front;
	Node<T> *rear;
};

template <class T>
LinkQueue<T>::LinkQueue()
{
	front = new Node<T>;
	front->next = NULL;
	rear = front;
}

template <class T>
LinkQueue<T>::~LinkQueue()
{
	Node<T> *p = front;
	while(p != rear)
	{
		p = p->next;
		delete front;
		front = p;
	}
	delete rear;
}

template <class T>
Status LinkQueue<T>::EnQueue(T e)
{
	Node<T> *p = new Node<T>;
	if(!p)
	{
		return ERROR;
	}
	p->data = e;
	p->next = NULL;
	rear->next = p;
	rear = p;	//修改尾指针
	return OK;
}

template <class T>
Status LinkQueue<T>::DeQueue(T &e)
{
	Node<T> *p;
	if(front == rear)
	{
		return ERROR;
	}
	p = front->next;
	e = p->data;
	front->next = p->next;
	if(rear == p)	//只有两个元素的情况，此时需要修改rear指针
	{
		rear = front;
	}
	delete p;
	return OK;
}

template <class T>
int LinkQueue<T>::QueueLength()
{
	int count = 0;
	Node<T> *p = front;
	while(p != rear)
	{
		++count;
		p = p->next;
	}
	return count;
}

template <class T>
Status LinkQueue<T>::IsEmpty()
{
	return (front == rear)?EMPTY:!EMPTY;
}

template <class T>
void LinkQueue<T>::DispQueue()
{
	Node<T> *p = front->next;
	while(p != NULL)
	{
		cout << p->data << " ";
		p = p->next;
	}
	cout<<endl;
}


int main()
{

	LinkQueue<int> queue1;
	cout << "Enter a queue!~" <<endl;
	for(int i=0; i<10; i++)
	{
		queue1.EnQueue(i);
	}
	queue1.DispQueue();
	cout << "The length of the queue is " << queue1.QueueLength()<<endl;
	int temp = 0;
	cout << "The first five nodes are out of the queue, they are: ";
	for(int i=0; i<5; i++)
	{
		queue1.DeQueue(temp);
		cout << temp << " ";
	}
	cout << endl;
	cout << "The rest of the queue are: ";
	queue1.DispQueue();
	cout << "Now, the length of the queue is " <<queue1.QueueLength()<<endl;
	cout << "The queue is empty? "<<queue1.IsEmpty()<<endl;
	for(int i=0; i<5; i++)
	{
		queue1.DeQueue(temp);
		cout << temp << " ";
	}
	queue1.DispQueue();
	cout << "The queue is empty? " << queue1.IsEmpty()<<endl;
	return 0;
}

队列的应用

//队列报数的例子
char *number(int n)
{
	char *result = new char;
	int i=0;
	int e = 0;
	CircularQueue<int> q;
	for(i=1; i<=n; i++)
	{
		q.EnQueue(i);
	}
	i = 0;
	//一个出队
	//接下来的一个先出队再进队
	while(q.IsEmpty() != EMPTY)
	{
		q.DeQueue(e);
		*(result + i++) = e+48;		//将字符变为数字
		if(q.IsEmpty() != EMPTY)
		{
			q.DeQueue(e);
			q.EnQueue(e);
		}
	}
	*(result + i) = '\0';
	return result;
}

队列小结

队列与栈的比较