用C实现队列

 队列是先入先出，用单链表实现比较方便，注意边界的处理

void QueueInit(Queue* pq)
{
	assert(pq);
	pq->head = pq->tail = NULL;
}
//销毁
void QueueDestroy(Queue* pq)
{
	assert(pq);
	QNode* cur = pq->head;
	while (cur)
	{
		QNode* next = cur->next;
		free(cur);
		cur = next;
	}
}
//入队列
void QueuePush(Queue* pq, QDataType x)
{
	assert(pq);
	QNode* newnode = (QNode*)malloc(sizeof(QNode));
	if (newnode == NULL)
	{
		printf("malloc failn");
		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;
	}
}
//出队列
void QueuePop(Queue* pq)
{
	assert(pq);
	assert(!QueueEmpty(pq));
	if (pq->head->next == NULL)		//对于只有一项的队列
	{
		free(pq->head);
		pq->head = pq->tail = NULL;
	}
	else
	{
		QNode* next = pq->head->next;
		free(pq->head);
		pq->head = next;
	}
}
//队头数据
QDataType QueueFront(Queue* pq)
{
	assert(!QueueEmpty(pq));
	assert(pq);
	return pq->head->data;
}
//队尾数据
QDataType QueueBack(Queue* pq)
{
	assert(!QueueEmpty(pq));
	assert(pq);
	return pq->tail->data;
}
//判断空
bool QueueEmpty(Queue* pq)
{
	assert(pq);
	return pq->head == NULL;		//判断头；
}
//数据个数的统计
int QueueSize(Queue* pq)
{
	assert(pq);
	int size = 0;
	QNode* cur = pq->head;
	while (cur)
	{
		size++;
		cur = cur->next;
	}

	return size;
}