doublyLinkedList.py

# Doubly Linked List implementation
# Create, Insert, Traverse, Search, Delete operations

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

class DoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None

    def __iter__(self):
        node = self.head
        while node:
            yield node
            node = node.next
    
    # Create
    def createDoublyLL(self, nodeValue):
        node = Node(nodeValue)
        node.prev = None
        node.next = None
        self.head = node
        self.tail = node
        return "The DoublyLL is created"
    

    # Insert
    def insertDoublyLL(self, nodeValue, location):
        if self.head is None:
            return "There is not any element in the list"
        else:
            newNode = Node(nodeValue)
            # Beginning
            if location == 0:
                newNode.prev = None
                newNode.next = self.head
                self.head.prev = newNode
                self.head = newNode
            # End
            elif location == 1:
                newNode.next = None
                newNode.prev = self.tail
                self.tail.next = newNode
                self.tail = newNode
            # Middle
            else:
                tempNode = self.head
                index = 0
                while index < location - 1:
                    tempNode = tempNode.next
                    index += 1
                newNode.next = tempNode.next
                newNode.prev = tempNode
                newNode.next.prev = newNode
                tempNode.next = newNode


    # Traverse
    def traverseDoublyLL(self):
        if self.head is None:
            return "There is not any element in the list"
        else:
            tempNode = self.head
            while tempNode:
                print(tempNode.value)
                tempNode = tempNode.next


    # Reverse Traverse
    def reverseTraverseDoublyLL(self):
        if self.head is None:
            return "There is not any element in the list"
        else:
            tempNode = self.tail
            while tempNode:
                print(tempNode.value)
                tempNode = tempNode.prev


    # Search
    def searchDoublyLL(self, nodeValue):
        if self.head is None:
            return "There is not any element in the list"
        else:
            tempNode = self.head
            while tempNode:
                if tempNode.value == nodeValue:
                    return tempNode.value
                tempNode = tempNode.next
            return "The node does not exist"


    # Delete
    def delete(self, location):
        if self.head is None:
            return "There is not any element in the list"
        else:
            # Beginning
            if location == 0:
                if self.head == self.tail:
                    self.head = None
                    self.tail = None
                else:
                    self.head = self.head.next
                    self.head.prev = None
            # End
            elif location == 1:
                if self.head == self.tail:
                    self.head = None
                    self.tail = None
                else:
                    self.tail = self.tail.prev
                    self.tail.next = None
            # Middle
            else:
                curNode = self.head
                index = 0
                while index < location - 1:
                    curNode = curNode.next
                    index += 1
                curNode.next = curNode.next.next
                curNode.next.prev = curNode
            print("The node is deleted")


    # Delete Entire DoublyLL
    def deleteEntireDoublyLL(self):
        if self.head is None:
            return "There is not any element in the list"
        else:
            tempNode = self.head
            while tempNode:
                tempNode.prev = None
                tempNode = tempNode.next
            self.head = None
            self.tail = None
            print("The DLL has been deleted")