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Program that implements a priority queue using an array

Posted By: Hedda Miller     Category: C Programming     Views: 33035

Program that implements a priority queue using an array.

Code for Program that implements a priority queue using an array in C Programming

#include <stdio.h>
#include <conio.h>

#define MAX 5

struct data
{
    char job[MAX] ;
    int prno ;
    int ord ;
} ;

struct pque
{
    struct data d[MAX] ;
    int front ;
    int rear ;
} ;

void initpque ( struct pque * ) ;
void add ( struct pque *, struct data ) ;
struct data delete ( struct pque * ) ;

void main( )
{
    struct pque q ;
    struct data dt, temp ;
    int i, j = 0 ;

    clrscr( ) ;

    initpque ( &q ) ;

    printf ( "Enter Job description (max 4 chars) and its priority\n" ) ;
    printf ( "Lower the priority number, higher the priority\n" ) ;
    printf ( "Job     Priority\n" ) ;

    for ( i = 0 ; i < MAX ; i++ )
    {
        scanf ( "%s %d", &dt.job, &dt.prno ) ;
        dt.ord = j++ ;
        add ( &q, dt ) ;
    }
    printf ( "\n" ) ;

    printf ( "Process jobs prioritywise\n" ) ;
    printf ( "Job\tPriority\n" ) ;

    for ( i = 0 ; i < MAX ; i++ )
    {
        temp  = delete ( &q ) ;
        printf ( "%s\t%d\n", temp.job, temp.prno ) ;
    }
    printf ( "\n" ) ;

    getch( ) ;
}

/* initialises data members */
void initpque ( struct pque *pq ) { int i ; pq -> front = pq -> rear = -1 ; for ( i = 0 ; i < MAX ; i++ ) { strcpy ( pq -> d[i].job, '\0' ) ; pq -> d[i].prno = pq -> d[i].ord = 0 ; } } /* adds item to the priority queue */
void add ( struct pque *pq, struct data dt ) { struct data temp ; int i, j ; if ( pq -> rear == MAX - 1 ) { printf ( "\nQueue is full." ) ; return ; } pq -> rear++ ; pq -> d[pq -> rear] = dt ; if ( pq -> front == -1 ) pq -> front = 0 ; for ( i = pq -> front ; i <= pq -> rear ; i++ ) { for ( j = i + 1 ; j <= pq -> rear ; j++ ) { if ( pq -> d[i].prno > pq -> d[j].prno ) { temp = pq -> d[i] ; pq -> d[i] = pq -> d[j] ; pq -> d[j] = temp ; } else { if ( pq -> d[i].prno == pq -> d[j].prno ) { if ( pq -> d[i].ord > pq -> d[j].ord ) { temp = pq -> d[i] ; pq -> d[i] = pq -> d[j] ; pq -> d[j] = temp ; } } } } } } /* removes item from priority queue */
struct data delete ( struct pque *pq ) { struct data t ; strcpy ( t.job, "" ) ; t.prno = 0 ; t.ord = 0 ; if ( pq -> front == -1 ) { printf ( "\nQueue is Empty.\n" ) ; return t ; } t = pq -> d[pq -> front] ; pq -> d[pq -> front] = t ; if ( pq -> front == pq -> rear ) pq -> front = pq -> rear = -1 ; else pq -> front++ ; return t ; }
  
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Hedda Miller
Hedda Miller author of Program that implements a priority queue using an array is from Frankfurt, Germany.
 
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