我创建了一个程序来实现带有插入，删除和显示的循环队列。插入工作正常并删除，但一旦我尝试删除后输入数字，则不显示任何内容。这是我的源代码：
#include<stdio.h>
#include<conio.h>
#define SIZE 5
int front = -1;
int rear = -1;
int queue[SIZE];
void enqueue(int item);
int dequeue();
void display();
void main()
{
int item, choice, cont = 1;
clrscr();
while(cont == 1)
{
printf("\n1.Enqueue into queue.\n");
printf("\n2.Dequeue from queue.\n");
printf("\n3.display quesue elements\n");
printf("\nEnter your choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("\nEnter the value of item: ");
scanf("%d",&item);
enqueue(item);
break;
case 2:
item = dequeue();
if(item != NULL)
{
printf("\nItem dequeued: %d\n",item);
}
break;
case 3:
display();
break;
default:
printf("\nInvalid choice.\n");
break;
}
printf("\nDo you want to continue (1/0): ");
scanf("%d",&cont);
}
getch();
}
void enqueue(int item)
{
if(front==0 && rear==SIZE-1)
printf("\n Queue OverFlow Occured");
else if(front==-1 && rear==-1)
{
front=rear=0;
queue[rear]=item;
}
else if(rear==SIZE-1 && front!=0)
{
rear=0;
queue[rear]=item;
}
else
{
rear++;
queue[rear]=item;
}
}
int dequeue()
{
int item = NULL;
if(front == -1 && rear == -1)
{
printf("\nQueue is empty. Dequeue not possible.\n");
}
else
{
item = queue[front];
queue[front] = NULL;
if(front == rear)
{
front = -1;
rear = -1;
}
else
{
front = front + 1;
}
}
return(item);
}
void display()
{
int i;
if(front==-1)
printf("\n No elements to display");
else
{
printf("\n The queue elements are:\n ");
for(i=front;i<=rear;i++)
{
printf("\t %d",queue[i]);
}
}
}
答案 0 :(得分：1)
检查此代码是否正常工作。
很少有建议不使用conio.h [clrscr（）和getch（）]这些都不是标准。
尝试下面的代码，对我来说很好。
#include<stdio.h>
#define SIZE 5
int front = -1;
int rear = -1;
int queue[SIZE];
void enqueue(int item);
int dequeue();
void display();
int main()
{
int item, choice, cont = 1;
while(cont == 1)
{
printf("\n1.Enqueue into queue.\n");
printf("\n2.Dequeue from queue.\n");
printf("\n3.display quesue elements\n");
printf("\nEnter your choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("\nEnter the value of item: ");
scanf("%d",&item);
enqueue(item);
break;
case 2:
item = dequeue();
if(item != NULL)
{
printf("\nItem dequeued: %d\n",item);
}
break;
case 3:
display();
break;
default:
printf("\nInvalid choice.\n");
break;
}
printf("\nDo you want to continue (1/0): ");
scanf("%d",&cont);
}
printf("");
return 0;
}
void enqueue(int item)
{
if(front==0 && rear==SIZE-1)
printf("\n Queue OverFlow Occured");
else if(front==-1 && rear==-1)
{
front=rear=0;
queue[rear]=item;
}
else if(rear==SIZE-1 && front!=0)
{
rear=0;
queue[rear]=item;
}
else
{
rear++;
queue[rear]=item;
}
}
int dequeue()
{
int item = NULL;
if(front == -1 && rear == -1)
{
printf("\nQueue is empty. Dequeue not possible.\n");
}
else
{
item = queue[front];
queue[front] = NULL;
if(front == rear)
{
front = -1;
rear = -1;
}
else
{
front = front + 1;
}
}
return(item);
}
void display()
{
int i;
if(front==-1)
printf("\n No elements to display");
else
{
printf("\n The queue elements are:\n ");
for(i=front;i<=rear;i++)
{
printf("\t %d",queue[i]);
}
}
}
Do you want to continue (1/0): 1
1.Enqueue into queue.
2.Dequeue from queue.
3.display quesue elements
Enter your choice: 3
The queue elements are:
5 5
Do you want to continue (1/0): 1
1.Enqueue into queue.
2.Dequeue from queue.
3.display quesue elements
Enter your choice: 1
Enter the value of item: 43
Do you want to continue (1/0): 1
1.Enqueue into queue.
2.Dequeue from queue.
3.display quesue elements
Enter your choice: 3
The queue elements are:
5 5 43
Do you want to continue (1/0): 1
1.Enqueue into queue.
2.Dequeue from queue.
3.display quesue elements
Enter your choice: 2
Item dequeued: 5
Do you want to continue (1/0): 1
1.Enqueue into queue.
2.Dequeue from queue.
3.display quesue elements
Enter your choice: 3
The queue elements are:
5 43
Do you want to continue (1/0):
答案 1 :(得分：1)
这是您的全功能更新代码。我在Ideone.com上粘贴代码链接为 link to code
如果你不理解任何事情，请问。我试图用评论来解释它。现在它没有遇到任何问题。
#include<stdio.h>
#include<conio.h>
#define SIZE 5
int front = -1;
int rear = -1;
int queue[SIZE];
void enqueue(int item);
int dequeue();
void display();
void main()
{
int item, choice, cont = 1;
clrscr();
while(cont == 1)
{
printf("\n1.Enqueue into queue.\n");
printf("\n2.Dequeue from queue.\n");
printf("\n3.display quesue elements\n");
printf("\nEnter your choice: ");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("\nEnter the value of item: ");
scanf("%d",&item);
enqueue(item);
break;
case 2:
item = dequeue();
if(item != NULL)
{
printf("\nItem dequeued: %d\n",item);
}
break;
case 3:
display();
break;
default:
printf("\nInvalid choice.\n");
break;
}
printf("\nDo you want to continue (1/0): ");
scanf("%d",&cont);
}
getch();
}
void enqueue(int item)
{
int temp = (rear+1)%SIZE; //EDIT HERE
if(temp == front){
printf("\n Queue OverFlow Occured");
return;
}
else if(front==-1 )
{
front=rear=0;
queue[rear]=item;
return;
}
else{
rear = (rear+1)%SIZE; // EDIT HERE
queue[rear%SIZE]=item;
}
}
int dequeue()
{
int item = NULL;
if(front == rear) // modified condition
{
printf("\nQueue is empty. Dequeue not possible.\n");
}
else
{
item = queue[front];
queue[front] = NULL;
front++; // front must be incremented
if(front > rear)
{
front = -1;
rear = -1;
}
}
return(item);
}
void display()
{
int i;
if(front==-1)
printf("\n No elements to display");
else
{
printf("\n The queue elements are:\n ");
for(i=front;i<=rear;i++)
{
printf("%d\t",queue[i]);
}
}
}
答案 2 :(得分：1)
这是一个相当混乱的代码。由于想法是让队列成为循环，因此通过检查front和rear的位置来尝试确定队列是否已满可能非常棘手，并且尝试根据{{做出决策1}}高于front等等。你可以避免这一切。跟踪队列长度的第三个变量将使您的生活变得更加轻松。
请尝试使用此实现：
rear