循环队列

课程来源mooc西北大学数据结构

基本思路 取模运算 

判空条件front==rear

判满条件 （rear+1）%MAXSIZE==front

队列长度 

① rear>front

rear-front个

① rear<front

(rear-front+MAXSIZE)%MAXSIZE

综上 个数等于（rear-front+MAXSIZE）%MAXSIZE

typedef struct SeqQueue
{
	int element[MAXSIZE];
	int front;
	int rear;
}SeqQueue,*PSeqQueue;

void InitSQ(PSeqQueue &Q)
{
	Q->front = Q->rear=0;//initialization
}

bool IsEmpty(const PSeqQueue &Q)
{
	if (Q->front == Q->rear)
		return true;
	return false;
}

bool EnterQueue(PSeqQueue &Q,int x)
{
	if ((Q->rear + 1) % MAXSIZE == Q->front)//Is full?
	{
		cout << "The SeqQueue is full!" << endl;
		return false;
	}
	Q->element[Q->rear] = x;
	Q->rear = (Q->rear + 1)%MAXSIZE;//rear++ most rear is MAXSIZE-1;
	return true;
}

bool DeleteQueue(PSeqQueue &Q, int *x)
{
	if (IsEmpty(Q))
	{
		cout << "The SeqQueue is empty!" << endl;
		return false;
	}
	*x = Q->element[Q->front];
	Q->front = (Q->front + 1) % MAXSIZE; //front++;
}

int LengthQueue(const PSeqQueue &Q)
{
	return (Q->rear - Q->front + MAXSIZE) % MAXSIZE;
}