Dec 14, 2011

C Program for Simple ASC order Priority QUEUE Implementation

Data structures using C,Priority QUEUE is a abstract data type in which the objects are inserted with respect to certain priority. In this program, we created the simple ascending order priority queue, here items are inserted in ascending order. Read more about C Programming Language .
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#define SIZE 5            /* Size of Queue */
int PQ[SIZE],f=0,r=-1;       /* Global declarations */

PQinsert(int elem)
 {
 int i;       /* Function for Insert operation */
  if( Qfull()) printf("\n\n Overflow!!!!\n\n");
  else
   {
    i=r;
    ++r;
    while(PQ[i] >= elem && i >= 0) /* Find location for new elem */
     {
      PQ[i+1]=PQ[i];
      i--;
      }
     PQ[i+1]=elem;
   }
  }

int PQdelete()
 {                      /* Function for Delete operation */
  int elem;
  if(Qempty()){ printf("\n\nUnderflow!!!!\n\n");
  return(-1); }
  else
   {
   elem=PQ[f];
   f=f+1;
   return(elem);
   }
 }

 int Qfull()
  {                     /* Function to Check Queue Full */
    if(r==SIZE-1) return 1;
    return 0;
  }

 int Qempty()
  {                    /* Function to Check Queue Empty */
    if(f > r) return 1;
    return 0;
  }

  display()
   {                  /* Function to display status of Queue */
    int i;
    if(Qempty()) printf(" \n Empty Queue\n");
    else
     {
      printf("Front->");
      for(i=f;i<=r;i++)
 printf("%d ",PQ[i]);
      printf("<-Rear");
     }
   }

  main()
  {                         /* Main Program */
   int opn,elem;
   do
    {
     clrscr();
     printf("\n ### Priority Queue Operations(ASC order) ### \n\n");
     printf("\n Press 1-Insert, 2-Delete,3-Display,4-Exit\n");
     printf("\n Your option ? ");
     scanf("%d",&opn);
     switch(opn)
      {
       case 1: printf("\n\nRead the element to be Inserted ?");
        scanf("%d",&elem);
        PQinsert(elem); break;
       case 2: elem=PQdelete();
        if( elem != -1)
    printf("\n\nDeleted Element is %d \n",elem);
        break;
       case 3: printf("\n\nStatus of Queue\n\n");
        display(); break;
       case 4: printf("\n\n Terminating \n\n"); break;
       default: printf("\n\nInvalid Option !!! Try Again !! \n\n");
  break;
      }
      printf("\n\n\n\n  Press a Key to Continue . . . ");
      getch();
      }while(opn != 4);
   }


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