隊(duì)列：只允許在一端進(jìn)行插入數(shù)據(jù)操作，在另一端進(jìn)行刪除數(shù)據(jù)操作的特殊線性表，隊(duì)列具有先進(jìn)先出FIFO(First In First Out) 入隊(duì)列：進(jìn)行插入操作的一端稱為隊(duì)尾出隊(duì)列：進(jìn)行刪除操作的一端稱為隊(duì)頭

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2. 隊(duì)列的實(shí)現(xiàn)

2.1 queue.h

#include<stdio.h>
#include<stdbool.h>
#include<assert.h>
#include<malloc.h>
typedef int QDataType;
typedef struct QueueNode
{
	struct QueueNode*next;
	QDataType data;
}QueueNode;
typedef struct Queue
{
	QueueNode *head;
	QueueNode *tail;
}Queue;
void QueueInit(Queue *pq);
void QueueDestory(Queue *pq);
void QueuePush(Queue *pq,QDataType x);
void QueuePop(Queue *pq);
QDataType QueueFront(Queue *pq);
QDataType QueueBack(Queue *pq);
bool QueueEmpty(Queue *pq);
int QueueSize(Queue *pq);

2.2 queue.c

#include"queue.h"
void QueueInit(Queue *pq)
{
	assert(pq);
	pq->head = pq->tail = NULL;
}
void QueueDestory(Queue *pq)
{
	assert(pq);
	QueueNode *cur = pq->head;
	while (cur)
	{
		QueueNode *next = cur->next;
		free(cur);
		cur = next;
	}
	pq->head = pq->tail = NULL;
}
void QueuePush(Queue *pq, QDataType x)
{
	assert(pq);
	QueueNode *newnode = (QueueNode*)malloc(sizeof(QueueNode));
	if (newnode == NULL)
	{
		printf("malloc fail\n");
		exit(-1);
	}
	newnode->data = x;
	newnode->next = NULL;
	if (pq->tail == NULL)
	{
		pq->head = pq->tail = newnode;
	}
	else
	{
		pq->tail->next = newnode;
		pq->tail = newnode;
	}
}
void QueuePop(Queue *pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	if (pq->head->next == NULL)
	{
		free(pq->head);
		pq->head = pq->tail = NULL;
	}
	else
	{
		QueueNode *next = pq->head->next;
		free(pq->head);
		pq->head = next;
	}
}
QDataType QueueFront(Queue *pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	return pq->head->data;
}
QDataType QueueBack(Queue *pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	return pq->tail->data;
}
bool QueueEmpty(Queue *pq)
{
	assert(pq);
	return pq->head == NULL;
}
int QueueSize(Queue *pq)
{
	int size = 0;
	QueueNode *cur = pq->head;
	while (cur)
	{
		QueueNode *next = cur->next;
		++size;
		cur = cur->next;
	}
	return size;
}

2.3 test.c

#include"queue.h"
void TestOne()
{
	Queue q;
	QueueInit(&q);
	QueuePush(&q, 1);
	QueuePush(&q, 2);
	QueuePush(&q, 3);
	QueuePush(&q, 4);
	while (!QueueEmpty(&q))
	{
		printf("%d  ", QueueFront(&q));
		QueuePop(&q);
	}
	printf("\n");
	QueueDestory(&q);
}
int main()
{
	TestOne();
	return 0;
}