Added adding operations on DoublyLL

Author: shreyasvedpathak

Linked List/doublyLL.py

@@ -0,0 +1,145 @@
+import os
+from typing import NewType, Sized
+
+class _Node:
+    __slots__ = '_element', '_link', '_prev'
+    def __init__(self, element, link, prev):
+        self._element = element
+        self._link = link
+        self._prev = prev
+    
+class DoublyLL:
+    def __init__(self):
+        self._head = None
+        self._tail = None
+        self._size = 0
+    
+    def __len__(self):
+        return self._size
+    
+    def isempty(self):
+        return self._size == 0
+
+    def addLast(self, e):
+        newest = _Node(e, None, None)
+
+        if self.isempty():
+            self._head = newest
+        else:
+            self._tail._link = newest
+            newest._prev = self._tail
+        self._tail = newest
+        self._size += 1
+
+    def addFirst(self, e):
+        newest = _Node(e, None, None)
+
+        if self.isempty():
+            self._head = newest
+            self._tail = newest
+        else:
+            newest._link = self._head
+            self._head._prev = newest
+        self._head = newest
+        self._size += 1
+
+    def addAnywhere(self, e, index):
+        if index >= self._size:
+            print(f'Index value out of range, it should be between 0 - {self._size - 1}')
+        elif self.isempty():
+            print("List was empty, item will be added at the end")
+            self.addLast(e)
+        elif index == 0:
+            self.addFirst(e)
+        elif index == self._size - 1:
+            self.addLast(e)
+        else:
+            newest = _Node(e, None, None)
+            p = self._head
+            for _ in range(index - 1):
+                p = p._link
+            newest._link = p._link
+            p._link._prev = newest
+            newest._prev = p
+            p._link = newest
+        self._size += 1
+
+
+    def display(self):
+        if self.isempty():
+            print("List is Empty")
+            return
+        
+        p = self._head
+        print("NULL<-->", end='')
+        while p:
+            print(p._element, end="<-->")
+            p = p._link
+        print("NULL")
+        print(
+            f"Head : {self._head._element}, Tail : {self._tail._element}")
+
+###############################################################################
+
+def options():
+    '''
+    Prints Menu for operations
+    '''
+    options_list = ['Add Last', 'Add First', 'Add Anywhere',
+                    'Remove First', 'Remove Last', 'Remove Anywhere',
+                    'Display List', 'Exit']
+
+    print("MENU")
+    for i, option in enumerate(options_list):
+        print(f'{i + 1}. {option}')
+
+    choice = int(input("Enter choice: "))
+    return choice
+
+
+def switch_case(choice):
+    '''
+    Switch Case for operations
+    '''
+    os.system('cls')
+    if choice == 1:
+        elem = int(input("Enter Item: "))
+        DL.addLast(elem)
+        print("Added Item at Last!\n\n")
+
+    elif choice == 2:
+        elem = int(input("Enter Item: "))
+        DL.addFirst(elem)
+        print("Added Item at First!\n\n")
+
+    elif choice == 3:
+        elem = int(input("Enter Item: "))
+        index = int(input("Enter Index: "))
+        DL.addAnywhere(elem, index)
+
+    elif choice == 4:
+        print("Removed Element from First:", DL.removeFirst())
+
+    elif choice == 5:
+        print("Removed Element from last:", DL.removeLast())
+
+    elif choice == 6:
+        index = int(input("Enter Index: "))
+        print(f"Removed Item: {DL.removeAnywhere(index)} !\n\n")
+
+    elif choice == 7:
+        print("List: ", end='')
+        DL.display()
+        print("\n")
+
+    elif choice == 8:
+        import sys
+        sys.exit()
+
+###############################################################################
+
+
+DL = DoublyLL()
+while True:
+    choice = options()
+    switch_case(choice)