circularDoublyLinkedList.py

# Circular 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 CircularDoublyLinkedList:
    def __init__(self):
        self.head = None
        self.tail = None

    def __iter__(self):
        node = self.head
        while node:
            yield node
            node = node.next
            if node == self.tail.next:
                break


    #  Create
    def createCircularDoublyLL(self, nodeValue):
        newNode = Node(nodeValue)
        self.head = newNode
        self.tail = newNode
        newNode.prev = newNode
        newNode.next = newNode
        return "The Circular Doubly LL is created"


    # Insert
    def insertCircularDoublyLL(self, value, location):
        if self.head is None:
            return "The Circular Doubly LL does not exist"
        else:
            newNode = Node(value)
            # Beginning
            if location == 0:
                newNode.next = self.head
                newNode.prev = self.tail
                self.head.prev = newNode
                self.head = newNode
                self.tail.next = newNode
            # End
            elif location == 1:
                newNode.next = self.head
                newNode.prev = self.tail
                self.head.prev = newNode
                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
            return "The node has been inserted"


    # Traverse
    def traverseCircularDoublyLL(self):
        if self.head is None:
            print("There is not any node")
        else:
            tempNode = self.head
            while tempNode:
                print(tempNode.value)
                if tempNode == self.tail:
                    break
                tempNode = tempNode.next


    # Reverse traverse
    def reverseTraverseCircularDoublyLL(self):
        if self.head is None:
            print("There is not any node")
        else:
            tempNode = self.tail
            while tempNode:
                print(tempNode.value)
                if tempNode == self.head:
                    break
                tempNode = tempNode.prev


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


    # Delete
    def deleteNode(self, location):
        if self.head is None:
            print("There is not any node")
        else:
            # Beginning
            if location == 0:
                if self.head == self.tail:
                    self.head.prev = None
                    self.head.next = None
                    self.head = None
                    self.tail = None
                else:
                    self.head = self.head.next
                    self.head.prev = self.tail
                    self.tail.next = self.head
            # End
            elif location == 1:
                if self.head == self.tail:
                    self.head.prev = None
                    self.head.next = None
                    self.head = None
                    self.tail = None
                else:
                    self.tail = self.tail.prev
                    self.tail.next = self.head
                    self.head.prev = self.tail
            # 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 has been deleted")


    # Delete Entire
    def deleteEntireCircularDoublyLL(self):
        if self.head is None:
            print("There is not any node")
        else:
            self.tail.next = None
            tempNode = self.head
            while tempNode:
                tempNode.prev = None
                tempNode = tempNode.next
            self.head = None
            self.tail = None
            print("The entire list has been deleted")