Queue Data Structure
Download as PPTX, PDF0 likes136 views
A queue is a first-in first-out (FIFO) data structure with two ends - one for inserting items and one for removing them. It uses two pointers, a front pointer pointing to the oldest item and a rear pointer pointing to the newest, empty slot. Items are inserted at the rear and removed from the front. Operations include enqueue to insert at the rear and dequeue to remove from the front, checking for overflow and underflow.
![CODE FOR INSERTION OPERATION
void insert(int data)
{
if (rear < arr.length - 1)
{
arr[++rear] = data;
System.out.println("Element " + data +" is inserted to
Queue !");
}
else
System.out.println("Overflow !");
}](https://image.slidesharecdn.com/queue-200527065427/85/Queue-Data-Structure-8-320.jpg)
![CODE FOR DELETION OPERATION
void delete()
{
if (rear >= front)
System.out.println("Deleted element=" +arr[front++]);
else
System.out.println("Underflow !");
}](https://image.slidesharecdn.com/queue-200527065427/85/Queue-Data-Structure-11-320.jpg)
Queue Data Structure
- 2. A queue is open at both its ends. One end is always used to insert data (enqueue) and the other is used to remove data (dequeue). Queue follows First In First Out (FIFO) methodology, i.e., the data item stored first will be accessed first. It has two pointers – front and rear. Front is used for deletion and rear is used for insertion. The difference between stack and queue is in removing the elements. In a stack we remove the item that has been recently added but in a queue, we remove the item that has been added at the first.
- 4. OPERATIONS OF QUEUE Insertion/Enqueue ( ) − Storing an element on the queue. Deletion/Dequeue ( ) − Removing an element from the queue. We also need to check the status of the queue to use it efficiently : Overflow – To check if queue is full. Underflow – To check if queue is empty.
- 6. ALGORITHM OF INSERTION OPERATION Step 1 − Start Step 2 – Check if the queue is full. Step 3 − If the queue is full, display Overflow. Step 4 − If the queue is not full, increment rear pointer to point to the next empty space. Step 5 − Add data element to the queue location, where the rear is pointing. Step 6 − End
- 7. IMPLEMENTATION OF INSERTION OPERATION 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 rea r rea r rea r rea r rear= - 1
- 8. CODE FOR INSERTION OPERATION void insert(int data) { if (rear < arr.length - 1) { arr[++rear] = data; System.out.println("Element " + data +" is inserted to Queue !"); } else System.out.println("Overflow !"); }
- 9. Step 1 − Start Step 2 – Check if the queue is empty. Step 3 − If the queue is empty, display Underflow. Step 4 − If the queue is not empty, access the data where front is pointing. Step 5 − Increment front pointer to point to the next available data element. Step 6 − End ALGORITHM OF DELETION OPERATION
- 10. 0 1 2 3 front= 0 rear=3 IMPLEMENTATION OF DELETION OPERATION 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 fro nt fro nt fro nt front= 4
- 11. CODE FOR DELETION OPERATION void delete() { if (rear >= front) System.out.println("Deleted element=" +arr[front++]); else System.out.println("Underflow !"); }