链队列的问题！

[时间一粒]

/*用单链表实现队列，如下图所示，并令front=rear=NULL表示队列为空，编写实现队列
的如下五种运算的函数。

Setnull:将队列置成空队列。

getfirst:返回队列的第一个元素。

enqueue:把元素插入队列的后端。

dequeue:删除队列的第一个元素。

empty:判定队列是否为空。*/

#include<stdio.h>
#include<stdlib.h>
#define OK 1
#define OVERFLOW -2
#define ERROR 0

typedef int ElemType;
typedef int Status;

typedef struct QNode{
   ElemType data;
   struct QNode *next;
} QNode, *QueuePtr;

typedef struct{
        QueuePtr front;
        QueuePtr rear;
        }LinkQueue; 
 
//判空
Status empty(LinkQueue Q)
{
  if(Q.front==Q.rear) return OK;
  else return ERROR; 
}
//置空
Status SetnullQueue(LinkQueue &Q) 
{
  Q.front=Q.rear=NULL;
  printf("队列为空!\n"); 
  exit(OVERFLOW); 
} 
//入队 
Status EnQueue(LinkQueue &Q,ElemType e)
{
  QueuePtr p=(QueuePtr)malloc(sizeof(QNode));
  if(!p)exit(OVERFLOW);
  p->data=e;
  p->next=NULL;
  Q.rear->next=p; 
  Q.rear=p; 
  return OK; 
} 
//出队
Status OutQueue(LinkQueue Q,ElemType &e)
 {
   QueuePtr p; 
   if(empty(Q))
     { exit(OVERFLOW);}//下溢
   else
   {  
     p=Q.front->next;
     Q.front->next=p->next;
     e=p->data;
     free(p);
     if(Q.front->next==NULL)
     Q.rear=Q.front ;
     return OK;
   }
   //return e;//返回原队头数据 
} 
///创建队列
Status InitQueue(LinkQueue &Q,int n)
{
  Q.front=Q.rear=(QueuePtr)malloc(sizeof(QNode));
  if(!Q.front)exit(OVERFLOW);
  Q.front->next=NULL;
  //Q.rear->next=NULL; 
  ElemType e; 
  for(int i=0;i<n;i++)
     { 
       scanf("%d",&e); 
       EnQueue(Q,e);
     } 
  return OK; 
} 
//取出队头元素
Status getfirst(LinkQueue Q,ElemType &e)
{
  QueuePtr p;
  if(empty(Q))
     { exit(OVERFLOW);}//下溢
  else{
       p=Q.front->next;
       e=p->data; 
      return e; 
      } 
   return OK;
} 
//删除队头元素 
Status dequeue(LinkQueue Q)
{
  ElemType e; 
  QueuePtr p;
  if(empty(Q)){exit(OVERFLOW);}
  else {
         p=Q.front->next;
         e=p->data;
         Q.front->next=p->next; 
         if(Q.rear==p) Q.rear=Q.front; 
         free(p);
         //printf("%d",e); 
       } 
       printf("\n"); 
     return OK; 
  } 
//插入元素
Status enqueue(LinkQueue &Q,ElemType e)
{
  QueuePtr p=(QueuePtr)malloc(sizeof(QNode));
  if(!p)exit(OVERFLOW);
  p->data=e;
  p->next=NULL; 
  Q.rear->next=p;
  Q.rear=p; 
  return OK; 
} 
//输出 
Status QPrint(LinkQueue Q,int n)
{
  ElemType e; 
  printf("队的元素为:"); 
      for(int k=0;k<n;k++) 
      { 
        OutQueue(Q,e);
        printf("%d ",e); 
      }
} 
//主函数 
 int main()
 {  
     int n; 
     ElemType e; 
     LinkQueue Q; 
     
     printf("Input the number you need:");
     scanf("%d",&n); 
     InitQueue(Q,n);
     //SetnullQueue(Q); 
     getfirst(Q,e);
     printf("队头元素:%d\n",e);
         
     printf("请输入要插入的元素:");
     scanf("%d",&e); 
     enqueue(Q,e);
     //n=; 
     QPrint(Q,n+1);
       
     
     
     printf("删除队头元素:");
     dequeue(Q);
     //n=n-1; 
     QPrint(Q,n-1);

      //empty(Q); 
     
      printf("\n");
     system("pause"); 
 } 

运行结果出错！

[yuanzhang198711]

去掉程序中所有的取地址符，基本上已经没什么问题。至于道理，你自己想想，在指针结构面前加&，你的目的是什么？你是传参吗？

[yuanzhang198711]

有点错误，是你定义的函数中的形参表中的取地址符。

[OnlyOB]

形参表中的取地址符再检查下

[Awang_126]

因为你在 QPrint(Q,n+1)中边显示每个节点数据，同时释放其空间，
所以你后面再执行
printf("删除队头元素:");
dequeue(Q);
//n=n-1;
QPrint(Q,n-1); //这里有问题 之前显示的时候已经释放空间了，你这里却还想显示，故有问题

[Awang_126]

#include <stdio.h>
#include<stdlib.h>
#define OK 1
#define OVERFLOW -2
#define ERROR 0

typedef int ElemType;
typedef int Status;

typedef struct QNode{
ElemType data;
struct QNode *next;
} QNode, *QueuePtr;

typedef struct{
QueuePtr front;
QueuePtr rear;
}LinkQueue;

//判空
Status empty(LinkQueue Q)
{
if(Q.front==Q.rear) return OK;
else return ERROR;
}
//置空
Status SetnullQueue(LinkQueue &Q)
{
Q.front=Q.rear=NULL;
printf("队列为空!\n");
exit(OVERFLOW);
}
//入队
Status EnQueue(LinkQueue &Q,ElemType e)
{
QueuePtr p=(QueuePtr)malloc(sizeof(QNode));
if(!p)exit(OVERFLOW);
p->data=e;
p->next=NULL;
Q.rear->next=p;
Q.rear=p;
return OK;
}
//出队
Status OutQueue(LinkQueue Q,ElemType &e)
{
QueuePtr p;
if(empty(Q))
{ exit(OVERFLOW);}//下溢
else
{
p=Q.front->next;
Q.front->next=p->next;
e=p->data;
free(p);
if(Q.front->next==NULL)
Q.rear=Q.front ;
return OK;
}
//return e;//返回原队头数据
}
///创建队列
Status InitQueue(LinkQueue &Q,int n)
{
Q.front=Q.rear=(QueuePtr)malloc(sizeof(QNode));
if(!Q.front)exit(OVERFLOW);
Q.front->next=NULL;
//Q.rear->next=NULL;
ElemType e;
for(int i=0;i<n;i++)
{
scanf("%d",&e);
EnQueue(Q,e);
}
return OK;
}
//取出队头元素
Status getfirst(LinkQueue Q,ElemType &e)
{
QueuePtr p;
if(empty(Q))
{ exit(OVERFLOW);}//下溢
else{
p=Q.front->next;
e=p->data;
return e;
}
return OK;
}
//删除队头元素
Status dequeue(LinkQueue Q)
{
ElemType e;
QueuePtr p;
if(empty(Q)){exit(OVERFLOW);}
else {
p=Q.front->next;
e=p->data;
Q.front->next=p->next;
if(Q.rear==p) Q.rear=Q.front;
free(p);
//printf("%d",e);
}
printf("\n");
return OK;
}
//插入元素
Status enqueue(LinkQueue &Q,ElemType e)
{
QueuePtr p=(QueuePtr)malloc(sizeof(QNode));
if(!p)exit(OVERFLOW);
p->data=e;
p->next=NULL;
Q.rear->next=p;
Q.rear=p;
return OK;
}
//输出
void QPrint(LinkQueue Q,int n)
{
ElemType e;
printf("队的元素为:");
for(int k=0;k<n;k++)
{
OutQueue(Q,e);
printf("%d ",e);
}
}
//主函数
void main()
{
int n;
ElemType e;
LinkQueue Q;

printf("Input the number you need:");
scanf("%d",&n);
InitQueue(Q,n);
//SetnullQueue(Q);
getfirst(Q,e);
printf("队头元素:%d\n",e);

printf("请输入要插入的元素:");
scanf("%d",&e);
enqueue(Q,e);
//n=;
QPrint(Q,n+1);



//printf("删除队头元素:");
// dequeue(Q);
// n=n-1;
// QPrint(Q,n-1);

//empty(Q);

printf("\n");
system("pause");
}

[时间一粒]

谢谢各位帮忙！

[yuanzhang198711]

这是我临时做的一个链队的程序。

/*queue.c*/
#include <stdio.h>
#include <stdlib.h>

typedef struct Node *link;


struct Node {
	unsigned char item;
	link next; /*pointer the next node */
};

static link head = NULL;	/*create the head node of list,and it is null */

static link front = NULL; /*front pointer of queue */

/*create a simple node,it is not in the list*/
link make_node(unsigned char item) {
	link p = malloc(sizeof(*p));

	p->item = item;
	p->next = NULL;
	return p;
}

/*release the space of the node*/
void free_node(link p)
{
	free(p);
}

/*clear all the node,and release the space*/
void destroy(void)
{
	link q, p = head;

	head = NULL;
	while (p) {
		q = p;
		p = p->next;
		free_node(q);
	}
}

/*add a node to the tail*/
void add(link p){
  if(head==NULL){
        head=p;
    }
   else{
      link q=head;
      link r;
    /*find the tail*/
     while(q){
       r=q->next;/*record the tail node*/
       q=q->next;
     }
     /*add the node to the tail*/
     p=r;
   }
}

/*delete a node in the list*/
void delete(link p)
{
	link pre;

	if (p == head) {
		head = p->next;
	}

	/*find the node ,then delete it */
	for (pre = head; pre; pre = pre->next)
		if (pre->next == p) {
			pre->next = p->next;
			return;
		}

}//end list.

/*region of queue*/

//enqueue,or let node in the queue.
void enqueue(unsigned char item) {
	link p = make_node(item);
	if (front == NULL) {
		front = p;
	}
	add(p);
	printf("enqueue success!\n");
}

//dequeue,ro let node out the queue.
void dequeue() {
	if (front == NULL) {
		link tmp = front;
		delete(front);
		front = tmp->next;
		printf("dequeue a front is :%d\n", tmp->item);
	}
	printf("queue has no items!\n");
}

//get the front node.
unsigned char peek() {
	if (front != NULL) {
		return front->item;
	} else {
		printf("queue has no items!\n");
	}
}

//clear all node.
void dequeueAll() {
	destroy();
}

void print_item(link p) {
	printf("%d\n", p->item);
}

int main(void) {
	enqueue(200);
	enqueue(100);
	enqueue(55);
	printf("The front of the queue is %d\n", peek());
	return 0;
}