队列实现

队列(queue): 一种先进先出(first in first out)FIFO的线性表
只允许在表的一端进行插入，而在表的另一端删除元素。

实现：

#include <stdio.h>
#include <stdlib.h>

typedef int QElemType;
typedef struct QNode{
	QElemType data;
	struct QNode *next;
}QNode, *QueuePtr; 
typedef struct{
	QueuePtr front;
	QueuePtr rear;
}LinkQueue;

int InitQueue(LinkQueue &Q){
	Q.front = Q.rear = (QueuePtr)malloc(sizeof(QNode));
	if (!Q.front)
		exit(-1);
	Q.front->next = NULL;
	return 1;
}

int EnQueue(LinkQueue &Q, QElemType e){
	QueuePtr p = (QueuePtr)malloc(sizeof(QNode));
	if (!p){
		exit(-1);
	}
	p->data = e;
	p->next = NULL;
	Q.rear->next = p;
	Q.rear = p;
	return 1;
}

int DeQueue(LinkQueue &Q, QElemType &e){
	if (Q.front == Q.rear)
		return -1;
	QueuePtr p = Q.front->next;
	e = p->data;
	Q.front->next = p->next;
	if (Q.rear == p)
		Q.rear = Q.front;
	free(p);
	return 1;
}

int DestroyQueue(LinkQueue &Q){
	while (Q.front){
		Q.rear = Q.front->next;
		free(Q.front);
		Q.front = Q.rear;
	}
	return 1;
}

int ClearQueue(LinkQueue &Q){
	Q.front = Q.rear;
	Q.front->next = NULL;
	return 1;
}

int QueueEmpty(LinkQueue Q){
	return (Q.front->next ==NULL &&  Q.rear->next == NULL) ? 1 : 0;
}
int QueueLength(LinkQueue Q){
	int length=0;
	QueuePtr p = Q.front->next;
	while (p){
		length++;
		p = p->next;
	}
	return length;
}
int GetHead(LinkQueue &Q, QElemType &e){
	e = Q.front->next->data;
	return 1;
}
int QueueTraverse(LinkQueue Q, int (*visit)(QueuePtr p)){
	QueuePtr p = Q.front->next;
	while(p){
		visit(p);
		p = p->next;
	}
	printf("\n");
	return 1;
}
int data_output(QueuePtr p){
	printf("%d  ", p->data);
	return 1;
}
int main(){
	int data,data2;
	LinkQueue Q;
	InitQueue(Q);
	int a[5] = { 0, 1, 2, 3, 4 };
	for (int i = 0; i < 5; i++){
		EnQueue(Q, i);
	}
	QueueTraverse(Q, data_output);
	DeQueue(Q, data);
	printf("出队%d\n", data);
	QueueTraverse(Q, data_output);
	printf("长度%d\n", QueueLength(Q));
	if (!(GetHead(Q, data2))){
		printf("error");
		return -1;
	}
	printf("头结点%d\n", data2);
	return 0;
}