lab_circularqueue_using_array.c

# include<stdio.h> 
# define MAX 5 
int cqueue_arr[MAX]; 
int front = -1; 
int rear = -1; 
/*Begin of insert*/ 
void insert(int item) 
{ 
if((front == 0 && rear == MAX-1) || (front == rear+1)) 
{ 
printf("Queue Overflow \n"); 
return; 
} 
if (front == -1) /*If queue is empty */ 
{ 
front = 0; 
rear = 0; 
} 
else 
{ 
if(rear == MAX-1) /*rear is at last position of queue */ rear = 0; 
else 
rear = rear+1; 
} 
cqueue_arr[rear] = item ; 
} 
/*End of insert*/ 
/*Begin of del*/ 
void del()
{ 
if (front == -1) 
{ 
printf("Queue Underflow\n"); 
return ; 
} 
printf("Element deleted from queue is : %d\n",cqueue_arr[front]); if(front == rear) /* queue has only one element */ 
{ 
front = -1; 
rear=-1; 
} 
else 
{ 
if(front == MAX-1) 
front = 0; 
else 
front = front+1; 
} 
} 
/*End of del() */ 
/*Begin of display*/ 
void display() 
{ 
int front_pos = front,rear_pos = rear; 
if(front == -1) 
{ 
printf("Queue is empty\n"); 
return; 
}
printf("Queue elements :\n"); 
if( front_pos <= rear_pos ) 
while(front_pos <= rear_pos) 
{ 
printf("%d ",cqueue_arr[front_pos]); 
front_pos++; 
} 
else 
{ 
while(front_pos <= MAX-1) 
{ 
printf("%d ",cqueue_arr[front_pos]); 
front_pos++; 
} 
front_pos = 0; 
while(front_pos <= rear_pos) 
{ 
printf("%d ",cqueue_arr[front_pos]); 
front_pos++; 
} 
} 
printf("\n"); 
} 
/*End of display*/ 
/*Begin of main*/ 
int main() 
{ 
int choice,item; 
do 
{
printf("1.Insert\n"); 
printf("2.Delete\n"); 
printf("3.Display\n"); 
printf("4.Quit\n"); 
printf("Enter your choice : "); 
scanf("%d",&choice); 
switch(choice) 
{ 
case 1 : 
printf("Input the element for insertion in queue : "); 
scanf("%d", &item); 
insert(item); 
break; 
case 2 : 
del(); 
break; 
case 3: 
display(); 
break; 
case 4: 
break; 
default: 
printf("Wrong choice\n"); 
} 
}while(choice!=4); 
return 0; 
}
/*End of main*/