What is stack ?

Stack

• Abstract data structure . It is higher level data structure . Because it is made using array and linked list .

It follows LIFO . Meaning if insert insert to top . If pop , Pop from top .

The data structure which follows LIFO is called stack .

Suppose we are inserting a value
10 - Top
Then 20
20 - Top
10

Then 30

30- Top
20
10

Let's Pop

20 - Top
10

Again pop

10 - Top

Again pop

NULL

In array we can remove value from any index . But we cannot do it in stack .

Let's take Linked List

10 -> 20 -> 30 -> 40

We can delete value at any position .

When we delete linked list using delete_at_tail function that time is deletion in stack .

So , The characteristic of STL -

1. Delete at tail
2. Insert at tail

Singly linked list delete_at_tail TC - O(N)
Doubly linked list delete_at_tail TC - O(1)
Array delete at tail TC- O(1)

Stack Operation -
-push()
-pop()
-top()
-size()
-empty()