LinkQueue

 

using namespace std;

#include <iostream>

#define OK 1
#define ERROR -1
#define TRUE 1
#define FALSE 0
#define OVERFLOW -2

typedef char QElemType;
typedef struct QNode {
	/************************************************************************/
	/*單鏈隊列存儲結構						         */
	/*Went 2011-11-2 10:08	       				       */
	/************************************************************************/
	QElemType data;
	struct QNode *next;
}QNode, *QueuePtr;
typedef struct {
	QueuePtr front;
	QueuePtr rear;
}LinkQueue;

int InitQueue(LinkQueue &Q) {
	//initiate an empty queue
	Q.front = Q.rear = (QueuePtr)malloc(sizeof(QNode));
	if (!Q.front)
		return OVERFLOW;
	Q.front -> next = NULL;
	return OK;
}

int DestroyQueue(LinkQueue &Q) {
	//destroy an existed queue
	if (Q.front == NULL)
		return ERROR;
	while(Q.front) {
		Q.rear = Q.front -> next;
		free(Q.front);
		Q.front = Q.rear;
	}
	return OK;
}

int ClearQueue(LinkQueue &Q) {
	//clear an exitstd queue
	if (Q.front == NULL) 
		return ERROR;
	QueuePtr p, q;
	Q.rear = Q.front;
	p = Q.front -> next;
	Q.front -> next = NULL;
	while(p) {
		q = p;
		p = p -> next;
		free(q);
	}
	return OK;
}

int QueueEmpty(LinkQueue Q) {
	//whether the queue is empty
	if (Q.front == NULL)
		return ERROR;
	else if (Q.front -> next == NULL)
		return TRUE;
	else
		return FALSE;
}

int QueueLenth(LinkQueue Q) {
	//get the length of the queue
	if (Q.front == NULL)
		return ERROR;
	int len = 0;
	QueuePtr p;
	p = Q.front;
	while(p != Q.rear) {
		len ++;
		p = p -> next;
	}
	return len;
}


int GetHead(LinkQueue Q, QElemType &e) {
	//get the head element of the queue
	if (Q.front == Q.rear)
		return ERROR;
	e = Q.front -> next -> data;
	return OK;
}

int EnQueue(LinkQueue &Q, QElemType e) {
	//input an element e as the new rear of the queue
	QueuePtr p;
	p = (QueuePtr)malloc(sizeof(QNode));
	if (!p)
		return OVERFLOW;
	p -> data = e;
	p -> next = NULL;
	Q.rear -> next = p;
	Q.rear = p;
	return OK;
}

int DeQueue(LinkQueue &Q, QElemType &e) {
	//delete an element which was the head of the queue
	if (Q.front == Q.rear)
		return ERROR;
	QueuePtr p;
	p = Q.front -> next;
	e = p -> data;
	Q.front -> next = p -> next;
	if (Q.rear == p)
		Q.rear = Q.front;
	free(p);
	return OK;
}

int visit(QElemType e) {
	cout << e << " ";
	return OK;
}

int QueueTraverse(LinkQueue Q, int (*visit)(QElemType)) {
	//visit the queue
	if (Q.front == NULL)
		return ERROR;
	QueuePtr p = Q.front -> next;
	while(p != NULL) {
		if (!visit(p -> data))
			return ERROR;
		p = p -> next;
	}
	cout << endl;
	return OK;
}

int main() {
	LinkQueue q1;
	QElemType e;
	InitQueue(q1);
	cout << QueueEmpty(q1) << endl;
	cout << QueueLenth(q1) << endl;
	EnQueue(q1, 'a');
	EnQueue(q1, 'b');
	GetHead(q1, e);
	cout << e << endl;
	cout << QueueEmpty(q1) << endl;
	cout << QueueLenth(q1) << endl;
	QueueTraverse(q1, visit);
	DeQueue(q1, e);
	cout << e << endl;
	QueueTraverse(q1, visit);
	system("pause");
	return 0;
}