In Python, I have to implement Double linked list where each node stores one lin

Question

In Python, I have to implement Double linked list where each node stores one line as a separate class to test the following functions for each class: (1) cmd_h: move cursor one character to the left (2) cmd_I: move cursor one character to the right (3) cmd_j: move cursor vertically one line (4) cmd_k: move cursor vertically one line (5) cmd_X: delete the character to the left of the cursor (6) cmd_D: remove on current line from cursor to the end (7) cmd_dd: delete current line and move cursor to the beginning of next line (8) cmd_ddp: transpose two adjacent lines (9) cmd_n: search for next occurrence of a string (assume that string to be searched is fully in one line. (10) cmd_wq: write your representation as text file and save it

Explanation / Answer

Double Linked List in Python

class Node(object):

    def __init__(self, data, previous, nxt):

        self.data = data

        self.previous = previous

        self.nxt = nxt

class DoubleLinkedList(object):

head = None

    tail = None

  def insert(self, data):

        new_node = Node(data, None, None)

        if self.head is None:

            self.head = self.tail = new_node

        else:

            new_node.previous = self.tail

            new_node.nxt = None

            self.tail.nxt = new_node

            self.tail = new_node

  def delete(self, node_value):

        current_node = self.head

  while current_node is not None:

            if current_node.data == node_value:

  if current_node.previous is not None:

                    current_node.previous.nxt = current_node.nxt

                    current_node.nxt.previous = current_node.previous

                else:

self.head = current_node.nxt

                    current_node.nxt.previous = None

            current_node = current_node.nxt

    def display(self):

        print "Display list data:"

        current_node = self.head

        while current_node is not None:

            print current_node.previous.data if hasattr(current_node.previous, "data") else None,

            print current_node.data,

            print current_node.nxt.data if hasattr(current_node.nxt, "data") else None

            current_node = current_node.nxt

        print "*"*50

d = DoubleLinkedList()

d.insert(5)

d.insert(6)

d.insert(50)

d.insert(30)

d.display()

d.delete(50)

d.delete(5)

d.display()

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