python doubly linked list code example

Example 1: linked list in python

class Node:
    def __init__(self, data = None, next_node = None):
        self.data = data
        self.nextNode = next_node

    def get_data(self):
        return self.data

    def set_data(self, data):
        self.data = data

    def get_nextNode(self):
        return self.nextNode

    def set_nextNode(self, nextNode):
        self.nextNode = nextNode


class LinkedList:
    def __init__(self, head = None):
        self.head = head


    def add_Node(self, data):
        # if empty
        if self.head == None:
            self.head = Node(data)


        # not empty
        else:
            curr_Node = self.head
            
            # if node added is at the start
            if data < curr_Node.get_data():
                self.head = Node(data, curr_Node)
                
            # not at start
            else:
                while data > curr_Node.get_data() and curr_Node.get_nextNode() != None:
                    prev_Node = curr_Node
                    curr_Node = curr_Node.get_nextNode()

                # if node added is at the middle
                if data < curr_Node.get_data():
                    prev_Node.set_nextNode(Node(data, curr_Node))
                

                # if node added is at the last
                elif data > curr_Node.get_data() and curr_Node.get_nextNode() == None:
                    curr_Node.set_nextNode(Node(data))



    def search(self, data):
        curr_Node = self.head
        while curr_Node != None:
            if data == curr_Node.get_data():
                return True

            else:
                curr_Node = curr_Node.get_nextNode()

        return False


    def delete_Node(self, data):
        if self.search(data):
            # if data is found

            curr_Node = self.head
            #if node to be deleted is the first node
            if curr_Node.get_data() == data:
                self.head = curr_Node.get_nextNode()

            else:
                while curr_Node.get_data() != data:
                    prev_Node = curr_Node
                    curr_Node = curr_Node.get_nextNode()
                    
                #node to be deleted is middle
                if curr_Node.get_nextNode() != None:
                    prev_Node.set_nextNode(curr_Node.get_nextNode())

                # node to be deleted is at the end
                elif curr_Node.get_nextNode() == None:
                    prev_Node.set_nextNode(None)

        else:
            return "Not found."

    def return_as_lst(self):
        lst = []
        curr_Node = self.head
        while curr_Node != None:
            lst.append(curr_Node.get_data())
            curr_Node = curr_Node.get_nextNode()

        return lst

    def size(self):
        curr_Node = self.head
        count = 0
        while curr_Node:
            count += 1
            curr_Node = curr_Node.get_nextNode()
        return count

      
## TEST CASES #
test1 = LinkedList()
test2 = LinkedList()
test1.add_Node(20)
test1.add_Node(15)
test1.add_Node(13)
test1.add_Node(14)
test1.delete_Node(17)
print(test1.return_as_lst())
print(test2.size())

Example 2: doubly linked list python

class ListNode:
    def __init__(self, value, prev=None, next=None):
        self.prev = prev
        self.value = value
        self.next = next

class DoublyLinkedList:
    def __init__(self, node=None):
        self.head = node
        self.tail = node
        self.length = 1 if node is not None else 0

    def __len__(self):
        return self.length
   
  	def add_to_head(self, value):
        new_node = ListNode(value, None, None)
        self.length += 1
        if not self.head and not self.tail:
            self.head = new_node
            self.tail = new_node
        else:
            new_node.next = self.head
            self.head.prev = new_node
            self.head = new_node
 
    def remove_from_head(self):
        value = self.head.value
        self.delete(self.head)
        return value

    def add_to_tail(self, value):
        new_node = ListNode(value, None, None)
        self.length += 1
        if not self.tail and not self.head:
            self.tail = new_node
            self.head = new_node
        else:
            new_node.prev = self.tail
            self.tail.next = new_node
            self.tail = new_node
            

    def remove_from_tail(self):
        value = self.tail.value
        self.delete(self.tail)
        return value
            
    def move_to_front(self, node):
        if node is self.head:
            return
        value = node.value
        if node is self.tail:
            self.remove_from_tail()
        else:
            node.delete()
            self.length -= 1
        self.add_to_head(value)
        
    def move_to_end(self, node):
        if node is self.tail:
            return
        value = node.value
        if node is self.head:
            self.remove_from_head()
            self.add_to_tail(value)
        else:
            node.delete()
            self.length -= 1
            self.add_to_tail(value)

    def delete(self, node):
        self.length -= 1
        if not self.head and not self.tail:
            return
        if self.head == self.tail:
            self.head = None
            self.tail = None
        elif self.head == node:
            self.head = node.next
            node.delete()
        elif self.tail == node:
            self.tail = node.prev
            node.delete()
        else:
            node.delete()

    def get_max(self):
        if not self.head:
            return None
        max_val = self.head.value
        current = self.head
        while current:
            if current.value > max_val:
                max_val = current.value
            current = current.next
        return max_val