circular queue

[ashokayengar]

A data representation that sequentially maps 'n' queues into an array First[Memory_Size]. Represent each queue as a circular queue within memory. Write functions to add and delete elements to queue and other functions to handle queue full situation.
How do I do this using pure 'C' coding .

I'am in great trouble please help me.

thanks.

[sally]

use a next available index for Insertion (ixIn) and a next available index for Retreival (ixOut)

when poking something in to the array check that ixOut is not equal to ixIn => full
if poking in is OK, insert the element into the array, and increment ixIn, making sure you use mod to wrap aroud to the beginning of the array

when taking something out of the array chack that the array is not empty
if it is not empty, take the element out, and increment ixOut, making sure you use mod to wrap aroud to the beginning of the array

it might need some improvement, but it is the basic design principle

sally

can u give me the code please in C i'will be greatfull to u

//Following code will help U
//Look this is for a single queue i.e not array of Queue . From your question found that u want
//array of queues , for this U will have to have 2-dimentional array i.e datatype queue[m][n]
//where 'm' is total number of queues & 'n' is the size of queue .
//now to the functions written by me where U are passing ptr to the queue pass ptr to 2-dimentional array
//& U will have to pass the queue number on which operations are to be done .
// so following is the code for single dimentional queue , hope it will help U .

//Following program is used to create circular queue

//Queue is of integers
//Comments :
//Queue follows First In Last Out model
//front always point to the one position less than latest element added &
//rear points to the last element of the queue


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


#define QUEUESIZE 4



int IsQueueFull(int front,int rear)//should be called while addding
{//returns 1 if queue is full
rear++ ;
rear = rear % QUEUESIZE ;
if (front == rear)
return 1 ;
return 0 ;
}

int IsQueueEmpty(int front,int rear)//should be called while deleting
{//return 1 when queue is empty
if (front == rear)
return 1 ;
return 0 ;
}

void add(int *queue,int* rear,int value)
{
(*rear)++ ;
*rear = *rear % QUEUESIZE ;
queue[*rear] = value ;
}

void del(int *queue,int* front,int *value)
{
(*front)++ ;
*front = *front % QUEUESIZE ;
*value = queue[*front] ;
}

void main()
{
int queue[QUEUESIZE],choice ;
int front , rear ,i ,value ;
front = rear = QUEUESIZE - 1 ;

while (1)
{
clrscr() ;
printf("Following are the options available for CIRCULAR Queue") ;
printf("\n1. Add") ;
printf("\n2. Delete") ;
printf("\n3. Exit") ;
printf("\n4. Display Queue") ;
printf("\n\n\t\tEnter your choice : ") ;
fflush(stdin) ;
scanf("%d",&choice) ;
switch (choice)
{
case 1:
if (!IsQueueFull(front,rear))
{
printf("\nEnter the value to be inserted : ") ;
fflush(stdin) ;
scanf("%d",&value) ;
add(queue,&rear,value) ;
printf("\n %d has been added to the queue",value );
}
else
printf("\nQueue is Full hence value cannot be added") ;
fflush(stdin) ;
getch() ;
break ;

case 2:
if (IsQueueEmpty(front,rear))
{
printf("\nQueue is empty hence no item is deleted") ;
}
else
{
del(queue,&front,&value) ;
printf("\nFollowing value is deleted from the queue : %d",value) ;
}
fflush(stdin) ;
getch() ;
break ;
case 3:
exit(0) ;
}
}
}


//my email id is [email protected]
//if need further help U can mail me there .U are welcome
//Even if U find any mistake in code do inform me as I have not compiled above code , just written

Yours
gautam

[sally]

Sorry, I have no C code, I just did the outline from memory
I used to write real time apps and we used them quite extensively then
but now I am elsewhere, and have no access to my old programs

sally

[Dave Lorde]

This would make a good homework question...

[ashokayengar]

thank u for ur valuable suggestion