# Insert node at beginning of Doubly linked list

The problem involves inserting a new node at the beginning of a doubly linked list. A doubly linked list is a data structure where each node contains a data element and two pointers, one pointing to the next node and another pointing to the previous node. Your task is to add a new node with a given value at the front of the doubly linked list.

## Problem Statement

Given a doubly linked list and a value, you need to insert a new node containing that value at the beginning of the list.

## Example

Consider the following example:

Suppose we are inserted the following (80,70,60,50,40,30,20,10) node in a sequence. ``NULL <- 10 <-> 20 <-> 30 <-> 40 <-> 50 <-> 60 <-> 70 -> NULL``

Value to be inserted: 5

After inserting the new node:

``NULL <- 5 <-> 10 <-> 20 <-> 30 <-> 40 <-> 50 <-> 60 <-> 70 -> NULL``

## Idea to Solve

To solve this problem, you need to create a new node with the given value and insert it at the beginning of the linked list. You will have to update the `next` and `prev` pointers of the new node and the previous head node to maintain the integrity of the doubly linked list.

## Pseudocode

``````insert(doublyLinkedList, value):
new_node = create_node(value)

## Algorithm Explanation

1. Create a new node using the `create_node` function with the given value.
2. Set the `next` pointer of the new node to the current `head` of the doubly linked list.
3. If the current `head` is not null (i.e., the list is not empty), update the `prev` pointer of the current `head` node to point to the new node.
4. Update the `head` of the doubly linked list to the new node.

## Time Complexity

The time complexity of this insertion algorithm is O(1), which means it's constant time. This is because inserting a node at the beginning of the doubly linked list involves only a few constant-time pointer updates, regardless of the size of the list.

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