Python program to search an element in a doubly linked list

When searching for an element in a doubly linked list, we need to create a Node class with three attributes: the data, a pointer to the next node, and a pointer to the previous node. We also need a main class to manage the list operations including adding nodes, displaying nodes, and searching for specific elements.

In a doubly linked list, each node has bidirectional pointers − one pointing to the next node and another to the previous node. This allows traversal in both directions, making it more flexible than a singly linked list.

Node Class Structure

The Node class represents individual elements in the doubly linked list ?

class Node:
    def __init__(self, my_data):
        self.previous = None
        self.data = my_data
        self.next = None

Doubly Linked List Implementation

Here's the complete implementation with search functionality ?

class Node:
    def __init__(self, my_data):
        self.previous = None
        self.data = my_data
        self.next = None

class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None
    
    def add_data(self, my_data):
        new_node = Node(my_data)
        if self.head == None:
            self.head = self.tail = new_node
            self.head.previous = None
            self.tail.next = None
        else:
            self.tail.next = new_node
            new_node.previous = self.tail
            self.tail = new_node
            self.tail.next = None
    
    def print_list(self):
        curr = self.head
        if self.head == None:
            print("The list is empty")
            return
        print("The nodes in the doubly linked list are:")
        while curr != None:
            print(curr.data)
            curr = curr.next
    
    def search_node(self, val_to_search):
        position = 1
        found = False
        curr = self.head
        
        if self.head == None:
            print("List is empty")
            return
        
        while curr != None:
            if curr.data == val_to_search:
                found = True
                break
            curr = curr.next
            position += 1
        
        if found:
            print(f"The node is present in the list at position: {position}")
        else:
            print("The node isn't present in the list")

# Create doubly linked list instance
dll = DoublyLinkedList()

print("Elements are being added to the doubly linked list")
dll.add_data(10)
dll.add_data(24)
dll.add_data(54)
dll.add_data(77)
dll.add_data(24)
dll.add_data(0)

dll.print_list()

print("The element 77 is being searched...")
dll.search_node(77)

print("The element 7 is being searched...")
dll.search_node(7)

Elements are being added to the doubly linked list
The nodes in the doubly linked list are:
10
24
54
77
24
0
The element 77 is being searched...
The node is present in the list at position: 4
The element 7 is being searched...
The node isn't present in the list

How the Search Works

The search algorithm follows these steps:

• Initialize − Start from the head node and set position counter to 1
• Traverse − Move through each node comparing data with the target value
• Track Position − Increment position counter for each node visited
• Return Result − Return position if found, otherwise indicate element not found

Key Features

Conclusion

Searching in a doubly linked list requires traversing nodes from head to tail until the target element is found. The search operation has O(n) time complexity, making it suitable for small to medium-sized datasets where bidirectional traversal is beneficial.