MOOC 2.3 队列

1. 循环队列

// 队列的顺序存储实现
#define MaxSize <存储数据元素的最大个数>
struct QNode
{
	ElementType Data[MaxSize];
	int rear;
	int front;
};
typedef struct QNode *Queue;

// 1. 入队
void AddQ(Queue PtrQ, ElementType item)
{
	if((PtrQ->rear + 1) % MaxSize == PtrQ->front)
	{
		printf("队列满");
		return ; 
	}
	PtrQ->rear = (PtrQ->rear + 1) % MaxSize;
	PtrQ->Data[PtrQ->rear] = item;
} 

// 2. 出队
ElementType DeleteQ(Queue PtrQ)
{
	if(PtrQ->front == PtrQ->rear)
	{
		printf("队列空");
		return REEOR;
	}
	else
	{
		PtrQ->front = (PtrQ->front + 1) % MaxSize;
		return PtrQ->Data[PtrQ->front];
	}
} 

　　

2. 链式队列

// 队列的链式存储
struct Node
{
	ElementType Data;
	struct Node *Next;
};
struct QNode
{
	struct Node *rear;
	struct Node *front;
};
typedef struct QNode *Queue;
Queue PtrQ;

ElementType DeleteQ(Queue PtrQ)
{
	struct Node *FrontCell;
	ElementType FrontElem;
	
	if(PtrQ->front == NULL)
	{
		printf("队列为空");
		return ERROR; 
	}
	FrontCell = PtrQ->front;
	if(PtrQ->front == PtrQ->rear)	// 队列只有一个元素 
	{
		PtrQ->front = PtrQ->rear = NULL;	// 删除后队列值为空 
	}
	else
	{
		PtrQ->front = PtrQ->front->Next;
	}
	FrontElem = FrontCell->Data;
	free(FrontCell);	// 释放被删除的结点空间 
	return FrontElem;
}

void AddQ(Queue PtrQ, ElementType item)
{
	struct Node node;
	node = (struct Node *)malloc(sizeof(struct Node));
	node->Data = item;
	node->Next = PtrQ->front->Next;
	PtrQ->front->Next = node;
}