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  1. #include<stdio.h>
  2. #include<conio.h>
  3. #define SIZE 5
  4. int front = -1;
  5. int rear = -1;
  6. int queue[SIZE];
  7. void enqueue(int item);
  8. int dequeue();
  9. void display();
  10. void main()
  11. {
  12.     int item, choice, cont = 1;
  13.     clrscr();
  14.  
  15.     while(cont == 1)
  16.     {
  17.         printf("\n1.Enqueue into queue.\n");
  18.         printf("\n2.Dequeue from queue.\n");
  19.         printf("\n3.display quesue elements\n");
  20.  
  21.         printf("\nEnter your choice: ");
  22.         scanf("%d",&choice);
  23.  
  24.         switch(choice)
  25.         {
  26.             case 1:
  27.                 printf("\nEnter the value of item: ");
  28.                 scanf("%d",&item);
  29.                 enqueue(item);
  30.                 break;
  31.  
  32.             case 2:
  33.                 item = dequeue();
  34.                 if(item != NULL)
  35.                 {
  36.                     printf("\nItem dequeued: %d\n",item);
  37.                 }
  38.                 break;
  39.          case 3:
  40.                 display();
  41.                 break;
  42.  
  43.             default:
  44.                 printf("\nInvalid choice.\n");
  45.                 break;
  46.         }
  47.  
  48.         printf("\nDo you want to continue (1/0): ");
  49.         scanf("%d",&cont);
  50.     }
  51.  
  52.     getch();
  53. }
  54.  
  55.  
  56. void enqueue(int item)
  57. {
  58.     int temp = (rear+1)%SIZE;    // EDIT HERE
  59.   if(temp == front ){
  60.     printf("\n Queue OverFlow Occured");
  61.     return;
  62.   }
  63.   else if(front==-1 )
  64.   {
  65.       front=rear=0;
  66.       queue[rear]=item;
  67.       return;
  68.   }
  69.   else{
  70.         rear = (rear+1)%SIZE;    // EDIT HERE
  71.         queue[rear]=item;
  72.    }
  73. }
  74. int dequeue()
  75. {
  76.     int item = NULL;
  77.     if( front == rear)   //     modified condition
  78.     {
  79.         printf("\nQueue is empty. Dequeue not possible.\n");
  80.     }
  81.     else
  82.     {
  83.         item = queue[front];
  84.         queue[front] = NULL;
  85.         front++;                                    // front must be incremented
  86.         if(front > rear)                           // front == rear means  1 element is left , it doesn't mean Queue is empty
  87.         {
  88.             front = -1;
  89.             rear = -1;
  90.         }
  91.    }
  92.     return(item);
  93. }
  94. void display()
  95. {
  96.     int i;
  97.     if(front==-1)
  98.       printf("\n No elements to display");
  99.     else
  100.     {
  101.       printf("\n The queue elements are:\n ");
  102.       for(i=front;i<=rear;i++)
  103.       {
  104.           printf("%d\t",queue[i]);
  105.       }
  106.     }
  107. }
  108.  
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.c:2:18: fatal error: conio.h: No such file or directory
compilation terminated.
stdout
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Standard output is empty
https://ideone.com/WAx8Ju
language:
C (gcc 8.3)
created:
9 years ago
visibility:
secret

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