implentation of queue using arrays

/* Implentation of queue using arrays */

# include "stdio.h"
# define SIZE 10

int arr[SIZE], front = -1, rear = -1, i ;
void enqueue() ;
void dequeue() ;
void display() ;

int main()
{
int ch ;
do
{
printf("\n[1].ENQUEUE [2].DEQUEUE [3].Display [4].Exit\n") ;
printf("Enter your choice [1-4] : ") ;
scanf("%d", &ch) ;
switch(ch)
{
case 1 :
enqueue() ;
break ;
case 2 :
dequeue() ;
break ;
case 3 :
display() ;
break ;
case 4 :
break ;
default :
printf("Invalid option\n") ;
}
} while(ch != 4) ;
}

void enqueue()
{
if(rear == SIZE - 1)
{
printf("Queue is full (overflow)\n") ;
return ;
}
rear++ ;
printf("Enter the element to ENQUEUE : ") ;
scanf("%d", &arr[rear]) ;
if(front == -1)
front++ ;
}

void dequeue()
{
if(front == -1)
{
printf("Queue is empty (underflow)\n");
return ;
}
printf("The DEQUEUE element is : %d\n", arr[front]) ;
if(front == rear)
front = rear = -1 ;
else
front++ ;
}

void display()
{
if(front == -1)
{
printf("Queue is empty (underflow)\n") ;
return ;
}
printf("The elements in queue are : FRONT -> ") ;
for(i = front ; i <= rear ; i++) printf(" ... %d", arr[i]) ; printf(" ... <- REAR\n") ; }

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