Queues 队列

1. Definiation

What is a queue?

A queue is a list. With a queue, inseration is done at one end (known as rear) whereas deletion is performed at the other end (known as front).

2. Operations

指针对列

无法自定义队长

// array queue
#include<iostream>
using namespace std;

struct Node
{
	int data;
};

class Queue
{
public:

	//初始化
	Queue()
	{
		front = -1;
		rear = -1;
	}

	//判断是否为空
	bool isEmpty()
	{
		if (rear == front)
			return true;
		return false;
	}

	//判队满
	bool isFull()
	{
		if (rear - front == 10)
			return true;
		return false;
	}

	//入队列
	void EnQueue(int item)
	{
		if (!isFull())
		{
			rear += 1;
			node[rear].data = item;
		}
		else
		{
			cout << "Full" << endl;
		}
	}

	//出队列
	void DiQueue()
	{
		if (!isEmpty())
		{
			front += 1;
		}
		else
		{
			cout << "Empty" << endl;
		}
	}

	//取队头
	int GetHead()
	{
		if (!isEmpty())
		{
			int temp = node[front+1].data;
			return temp;
		}
		else
		{
			cout << "Empty" << endl;
			return 0;
		}
	}

	//得队长
	int GetSize()
	{
		return rear - front;
	}

private:
	int front;   //队头指针总是指向队头元素的前一个位置
	int rear;
	Node node[10];
};

可自定义队长

//自己动手写queue
//array queue
template<typename Object>
struct Node
{
	Object data;
};

template<typename Object>
class Queue
{
public:
	//初始化
	Queue(int m)
	{
		init(m);
	}

	Queue&operator=(Queue&q)
	{
		if (this == &q)
			return *this;
		clear();
		for (int i = 0; i < q.curSize; i++)
			this->EnQueue(q.list[i].data);
		return *this;
	}

	Queue(Queue&q)
	{
		init(q.maxsize);
		*this = q;
	}

	//删除队列
	~Queue()
	{
		delete list;
	}

	//判断是否为空
	bool isEmpty()
	{
		if (curSize == 0)
			return true;
		return false;
	}

	//判队满
	bool isFull()
	{
		if (curSize == maxsize)
			return true;
		return false;
	}

	//入队列
	void EnQueue(int item)
	{
		if (!isFull())
		{
			rear += 1;
			list[rear].data = item;
			curSize++;
		}
		else
		{
			cout << "Full" << endl;
		}
	}

	//出队列
	void DiQueue()
	{
		if (!isEmpty())
		{
			front += 1;
			curSize--;
		}
		else
		{
			cout << "Empty" << endl;
		}
	}

	//取队头
	int GetHead()
	{
		if (!isEmpty())
		{
			int temp = list[front + 1].data;
			return temp;
		}
		else
		{
			cout << "Empty" << endl;
			return 0;
		}
	}

	//得队长
	int GetSize()
	{
		return curSize;
	}

	//清空队列
	void clear()
	{
		for (int i = 0; i<curSize; i++)
		{
			if (isEmpty())
			{
				return;
			}
			else
			{
				rear--;
			}
		}
		curSize = 0;
	}

private:
	int front;
	int rear;
	int maxsize;
	int curSize;
	Node<Object>* list;

	void init(int m)
	{
		front = -1;
		rear = -1;
		maxsize = m;
		curSize = 0;
		list = new Node<Object>[maxsize];
	}
};

　　

一般的数组队列会出现假溢出的问题，为了解决这个问题，我们可以利用循环队列

需要注意的是，你设计的队列大小与实际可以用到的队列大小是不一样的，总是-1

// circular queue
#include<iostream>
using namespace std;

struct Node
{
	int data;
};

class CirQueue
{
public:

	//初始化
	CirQueue()
	{
		rear = 3;
		front = 3;
	}

	//判空
	bool isEmpty()
	{
		if (front == rear)
			return true;
		return false;
	}

	//判满，牺牲队列的一个空间来判满
	bool isFull()
	{
		if ((rear + 1) % 4 == front)
			return true;
		return false;
	}

	//入队
	void EnQueue(int item)
	{
		if (!isFull())
		{
			rear = (rear + 1) % 4;
			node[rear].data = item;
		}
		else
		{
			cout << "Full" << endl;
		}
	}

	//出队
	void DiQueue()
	{
		if (!isEmpty())
		{
			front = (front + 1) % 4;
		}
		else
		{
			cout << "Empty" << endl;
		}
	}

	//取队头
	int GetHead()
	{
		if (!isEmpty())
		{
			return node[(front+1)%4].data;
		}
		else return -1;
	}
private:
	int front;
	int rear;
	Node node[4];
};

其实不用游标来判断队空与队满就不用牺牲一个空间了

//自己动手写queue
//circular queue
template<typename Object>
struct Node
{
	Object data;

	Node(const Object &d = Object()) :data(d){}
};

template<typename Object>
class CircularQueue
{
public:
	//the big three
	CircularQueue(int m)
	{
		init(m);
	}

	CircularQueue(CircularQueue& cq)
	{
		init(cq.maxSize);
		*this = cq;
	}

	~CircularQueue()
	{
		delete[] node;
	}

	CircularQueue& operator=(CircularQueue &cq)
	{
		if (this == &cq)
			return *this;
		clear();
		for (int i = 0; i<cq.curSize; i++)
			this->EnQueue(cq.node[i].data);
		return *this;
	}

	//判空
	bool isEmpty()
	{
		return curSize == 0;
	}

	//判满
	bool isFull()
	{
		return curSize == maxSize;
	}

	//入队
	void EnQueue(Object item)
	{
		if (!isFull())
		{
			curSize++;
		}
		rear = (rear + 1) % maxSize;
		node[rear].data = item;
	}

	//出队
	void DIQueue()
	{
		if (!isEmpty())
		{
			head = (head + 1) % maxSize;
			curSize--;
		}
	}

	//取队头
	Object GetHead()
	{
		return node[(head + 1) % maxSize].data;
	}

	//得队长
	int GetSize()
	{
		return curSize;
	}

	//清空队列
	void clear()
	{
		head = maxSize - 1;
		rear = maxSize - 1;
		curSize = 0;
	}

private:
	int head;
	int rear;
	int maxSize;
	int curSize;
	Node<Object>*node;

	void init(int m)
	{
		head = m - 1;
		rear = m - 1;
		maxSize = m;
		curSize = 0;
		node = new Node<Object>[maxSize];
	}
};

　　

　　

链表队列

就无什么假溢出的问题了

template<typename Type>
struct Node
{
	Type data;
	Node*next;
	Node*prev;

	Node(const Type& d = Type(), Node*p = NULL, Node *n = NULL) :data(d), prev(p), next(n){}
};


template<typename Type>
class Queue
{
public:
	Queue()
	{
		init();
	}

	Queue(Queue& q)
	{
		init();
		*this = q;
	}

	~Queue()
	{
		clear();
		delete head;
		delete tail;
	}

	const Queue& operator= (const Queue& q)
	{
		if (this == &q)
			return *this;
		clear();
		Node<Type>*p = q.head->next;
		while (p->next != q.tail)
		{
			this.EnQueue(p->data);
			p = p->next;
		}
		return *this;*/
	}
	
	bool IsEmpty()
	{
		return size == 0;
	}

	void EnQueue(Type item)
	{
		Node<Type>*p = new Node<Type>;
		p->data = item;
		p->prev = tail->prev;
		tail->prev->next = p;
		tail->prev = p;
		p->next = tail;
		size++;
	}

	void DIQueue()
	{
		if (!IsEmpty())
		{
			Node<Type>*p = head->next;
			head->next = p->next;
			p->next->prev = head;
			delete p;
			size--;
		}
	}

	Type GetHead()
	{
		return (head->next->data);
	}

	void clear()
	{
		while (head->next != tail)
		{
			DIQueue();
		}
		size = 0;
	}

	int GetSize()
	{
		return size;
	}

private:
	Node<Type>*tail;
    Node<Type>*head;
	int size;

	void init()
	{
		head = new Node<Type>;
		tail = new Node<Type>;
		head->next = tail;
		tail->prev = head;
		size = 0;
	}
};