#define SIZE 5            /* Size of Queue */
int f=0,r=-1;       /* Global declarations */
typedef struct PRQ
{
    int ele;
    int pr;
}PriorityQ;

PriorityQ PQ[SIZE];

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

PriorityQ PQdelete()
{                      /* Function for Delete operation */
    PriorityQ p;
    if(Qempty()){ printf("\n\nUnderflow!!!!\n\n");
    p.ele=-1;p.pr=-1;
    return(p); }
    else
    {
        p=PQ[f];
        f=f+1;
        return(p);
    }
}
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,%d] ",PQ[i].ele,PQ[i].pr);
        printf("<-Rear");
    }
}

main()
{                         /* Main Program */
    int opn;
    PriorityQ p;
    do
    {
        clrscr();
        printf("\n ### Priority Queue Operations(DSC 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 and its Priority?");
            scanf("%d%d",&p.ele,&p.pr);
            PQinsert(p.ele,p.pr); break;
        case 2: p=PQdelete();
            if( p.ele != -1)
                printf("\n\nDeleted Element is %d \n",p.ele);
            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);
}

The post C Program for Simple DSC order Priority QUEUE Implementation using Structure first appeared on Student Projects.

2. In case of structure, each member have their own memory space but In union, one block is used by all the member of the union.

Detailed Example:

struct stu
{
	char c;
	int l;
	float p;
};

union emp
{
	char c;
	int l;
	float p;
};

In the above example size of the structure stu is 7 and size of union emp is 4.

The post What is the differnce between Structure and Union? first appeared on Student Projects.