"双队列"学习

1.输入限制性双队列：

代码：InLimitDeQueue.c

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

typedef struct _queue
{
	int data;
	struct _queue *next;
}QUEUE;

QUEUE * rear = NULL;
QUEUE * front = NULL;

//输入限制型双队列
int InQueue(int value)
{
	QUEUE * q = (QUEUE *)malloc(sizeof(QUEUE));
	if(q == NULL) return 0;
	q->data = value;
	q->next = NULL;
	if(front == NULL)
		front = q;
	else
		rear->next = q;
	rear = q;
	return 1;
}

int OutQueueByFront(int *value)
{
	QUEUE * p = NULL;
	if(front == NULL)
		return 0;
	p = front;
	front = front->next;
	*value = p->data;
	free(p);
	return 1;
}

int OutQueueByRear(int *value)
{
	QUEUE *p = NULL;
	if(rear == NULL)
		return 0;
	//只有一个数据
	if(rear == front)
	{
		*value = rear->data;
		free(rear);
		rear = NULL;
		front = NULL;
	}else{
		p = front;
		//使p指向最后一个的前面一个
		while(p->next != rear)
			p = p->next;
		*value = rear->data;
		free(rear);
		rear = p;
		rear->next = NULL;
	}
	return 1;
}

void main()
{
	int res,i,arr[5] = {1,2,3,4,5};
	for(i = 0;i<5;i++)
		InQueue(arr[i]);
	while(1)
	{
		printf("1.从队头取出;2.从队尾取出;3.退出:");
		scanf("%d",&res);
		//清空输入缓冲区
		fflush(stdin);
		if(res == 1)
		{
			if(OutQueueByFront(&res) == 1)
				printf("取出的值为：%d\n",res);
			else
				printf("队列为空！\n");

		}else if(res == 2)
		{
			if(OutQueueByRear(&res) == 1)
				printf("取出的值为：%d\n",res);
			else
				printf("队列为空！\n");
		}else if(res == 3)
		{
			exit(0);
		}
	}
}

运行效果：

存入队列的元素为1，2，3，4，5

2.输出限制性双队列：

代码：OutLimitDeQueue.c

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

typedef struct _queue
{
	int data;
	struct _queue *next;
}QUEUE;

QUEUE * rear = NULL;
QUEUE * front = NULL;

//输出限制型双队列
int OutQueue(int *value)
{
	QUEUE *p = NULL;
	if(front == NULL)
		return 0;
	p = front;
	front = front->next;
	*value = p->data;
	free(p);
	return 1;
}

int InQueueByRear(int value)
{
	QUEUE *q = (QUEUE *)malloc(sizeof(QUEUE));
	if(q == NULL) return 0;
	q->data = value;
	q->next = NULL;
	if(rear == NULL)
		front = q;
	else 
		rear->next = q;
	rear = q;
	return 1;
}

int InQueueByFront(int value)
{
	QUEUE *q = (QUEUE *)malloc(sizeof(QUEUE));
	if(q == NULL)return 0;
	q->data = value;
	q->next = front;
	front = q;
	if(rear == NULL)
		rear = q;
	return 1;
}


void PrintQueue()
{
	QUEUE *p = front;
	while(p)
	{
		printf("%5d",p->data);
		p = p->next;
	}
	printf("\n");
}

void main()
{
	int res;
	while(1)
	{
		printf("1.从队头存入；2.从队尾存入；3.退出");
		scanf("%d",&res);
		fflush(stdin);
		if(res == 1)
		{
			printf("请输入要存入的值：");
			scanf("%d",&res);
			fflush(stdin);
			if(InQueueByFront(res))
			{
				PrintQueue();
			}else
				printf("存入失败\n");
		}else if(res == 2)
		{
			printf("请输入要存入的值：");
			scanf("%d",&res);
			fflush(stdin);
			if(InQueueByRear(res))
			{
				PrintQueue();
			}else
				printf("存入失败\n");
		}else if(res == 3)
			break;
	}
}

运行效果：