Double Ended Queue using an array
#include<stdio.h>#define MAX 5
int q[MAX];
int front = -1, rear= -1;
void insertAtRear(int item)
{
if ( rear == MAX - 1 )
{
printf ( "\nDequeue is overflow" );
}
else
{
if(front==-1 &&rear==-1)
front=rear=0;
else
rear=rear+1;
q[rear] = item;
}
}
void deleteAtFront()
{
int item;
if(front==-1)
printf("\nDequeue underflow");
else
{
item = q[front];
printf("\nItem deleted from queue is %d",item);
if(front == rear)
front = rear = -1;
else
front = front+1;
}
}
void insertAtFront(int item)
{
int i;
if( front == 0 && rear == MAX - 1 )
{
printf ( "\nDequeue is overflow" ) ;
}
else
{
if(front == -1 &&rear == -1)
{
front = rear = 0;
}
else if(front == 0 && rear>=0)
{
for(i = rear; i>=front; i--)
q[i+1] = q[i];
rear = rear+1;
}
else if(front != 0)
{
front = front - 1;
}
q[front]=item;
}
}
void deleteAtRear()
{
int item;
if(front==-1)
printf("\nDequeue underflow");
else
{
item = q[rear];
printf("\nItem deleted from queue is %d", item);
if(front == rear)
front = rear = -1;
else
rear = rear-1 ;
}
}
void display()
{
int i;
printf("\nfront = %d rear=%d", front, rear);
if(front == -1)
{
printf("\nEmpty");
return;
}
else
{
printf("\nContents are: \n");
for(i=front; i<=rear; i++)
printf("%d ", q[i]);
}
}
void main()
{
int ch, item;
while(1)
{
printf("\n\n~~Menu~~");
printf("\n1.Insert at front");
printf("\n2.Delete from front");
printf("\n3.Insert at rear");
printf("\n4.Delete at rear");
printf("\n5.Display");
printf("\n6.Exit");
printf("\nPlease enter a valid choice:");
scanf("%d",&ch);
switch(ch)
{
case 1: printf("\nEnter the item to be inserted: ");
scanf("%d", &item);
insertAtFront(item);
display();
break;
case 2: deleteAtFront();
display();
break;
case 3: printf("\nEnter the item to be inserted: ");
scanf("%d",&item);
insertAtRear(item);
display();
break;
case 4: deleteAtRear();
display();
break;
case 5: display();
break;
case 6: exit(0);
default: printf("\nEnter the valid choice: ");
break;
}
}
}
Output
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:1
Enter the item to be inserted: 11
front = 0 rear = 0
Contents are:
11
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:1
Enter the item to be inserted: 22
front = 0 rear = 1
Contents are:
22 11
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:1
Enter the item to be inserted: 33
front = 0 rear = 2
Contents are:
33 22 11
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:2
Item deleted from queue is 33
front = 1 rear = 2
Contents are:
22 11
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:2
Item deleted from queue is 22
front = 2 rear = 2
Contents are:
11
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:3
Enter the item to be inserted: 33
front = 2 rear = 3
Contents are:
11 33
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:1
Enter the item to be inserted: 22
front = 1 rear = 3
Contents are:
22 11 33
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:1
Enter the item to be inserted: 44
front = 0 rear = 3
Contents are:
44 22 11 33
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:3
Enter the item to be inserted: 55
front = 0 rear=4
Contents are:
44 22 11 33 55
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:3
Enter the item to be inserted: 77
Dequeue is overflow
front = 0 rear=4
Contents are:
44 22 11 33 55
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:4
Item deleted from queue is 55
front = 0 rear = 3
Contents are:
44 22 11 33
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:2
Item deleted from queue is 44
front = 1 rear = 3
Contents are:
22 11 33
~~Menu~~
1.Insert at front
2.Delete from front
3.Insert at rear
4.Delete at rear
5.Display
6.Exit
Please enter a valid choice:6
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