Programs that implement Queue (its operations) using Arrays.

#include<stdio.h>
#include<alloc.h>
#include<conio.h>
#define size 10
#define true 1
#define false 0

struct q_arr
{
int f,r;
int num;
int a[size];
};

void init(struct q_arr* queue);
int e_que(struct q_arr* queue);
int f_que(struct q_arr* queue);
int add_ele(struct q_arr* queue,int);
int rem_ele(struct q_arr* queue);
void display_ele(struct q_arr* queue);

/*main function*/
void main()
{
int ele,k;
int ch;

struct q_arr *queue = (struct q_arr*)malloc(sizeof(struct q_arr));
init(queue);

while(1)
{
clrscr();
printf("\n\n****IMPLEMENTATION OF QUEUE USING ARRAYS****\n");
printf("============================================");
printf("\n\t\tMENU\n");
printf("============================================");
printf("\n\t[1] To insert an element");
printf("\n\t[2] To remove an element");
printf("\n\t[3] To display all the elements");
printf("\n\t[4] Exit");
printf("\n\n\t Enter your choice: ");
scanf("%d",&ch);

switch(ch)
{
case 1:
{
printf("\nElement to be inserted:");
scanf("%d",&ele);
add_ele(queue,ele);
break;
}

case 2:
{
if(!e_que(queue))
{
k=rem_ele(queue);
printf("\n%d element is removed\n",k);
getch();
}
else
{
printf("\tQueue is Empty. No element can be removed.");
getch();
}
break;
}

case 3:
{
display_ele(queue);
getch();
break;
}

case 4:
exit(0);

default:
printf("\tInvalid Choice.");
getch();
break;
}
}
}
/*end main*/

void init(struct q_arr* queue)
{
queue->f = 0;
queue->r = -1;
queue->num = 0;
}

/* Function to check is the queue is empty*/
int e_que(struct q_arr* queue)
{
if(queue->num==0)
return true;
return false;
}

/* Function to check if the queue is full*/
int f_que(struct q_arr* queue)
{
if(queue->num == size)
return true;
return false;
}

/* Function to add an element to the queue*/
int add_ele(struct q_arr* queue,int j)
{
if(f_que(queue))
return false;

if(queue->r == size - 1)
queue->r = -1;
queue->a[++queue->r] = j;
queue->num++;
return true;
}

/* Function to remove an element of the queue*/
int rem_ele(struct q_arr* queue)
{
int j;
if(e_que(queue))
return -9999;
j = queue->a[queue->f++];
if(queue->f == size)
queue->f = 0;
queue->num--;
return j;
}

/* Function to display the queue*/
void display_ele(struct q_arr* queue)
{
int j;
if(e_que(queue))
{
printf("Queue is Empty. No records to display.");
return;
}
printf("\nElements present in the Queue are: ");
for(j=queue->f;j<=queue->r;j++)
printf("%d\t",queue->a[j]);
printf("\n");
}
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