Python Doubly Linked List:

class Node: def __init__(self, e, n, p): self.element = e self.next = n self.prev = p

class DoublyList: def __init__(self, a): # Creates a Non Dummy Headed Circular Doubly Linked List using the values from the given array a. # To Do pass # Remove this line # Counts the number of Nodes in the list and return the number def countNode(self): # To Do pass # Remove this line # prints the elements in the list def forwardprint(self): # To Do pass # Remove this line

# prints the elements in the list backward def backwardprint(self): # To Do pass # Remove this line

# returns the reference of the at the given index. For invalid index return None. def nodeAt(self, idx): # To Do pass # Remove this line # returns the index of the containing the given element. if the element does not exist in the List, return -1. def indexOf(self, elem): # To Do pass # Remove this line

# inserts containing the given element at the given index Check validity of index. def insert(self, elem, idx): # To Do pass # Remove this line # removes at the given index. returns element of the removed node. Check validity of index. return None if index is invalid. def remove(self, idx): # To Do pass # Remove this line

print("/// Test 01 ///") a1 = [10, 20, 30, 40] h1 = DoublyList(a1) # Creates a linked list using the values from the array

h1.forwardprint() # This should print: 10,20,30,40. h1.backwardprint() # This should print: 40,30,20,10. print(h1.countNode()) # This should print: 4

print("/// Test 02 ///") # returns the reference of the at the given index. For invalid idx return None. myNode = h1.nodeAt(2) print(myNode.element) # This should print: 30. In case of invalid index This will print "index error"

print("/// Test 03 ///") # returns the index of the containing the given element. if the element does not exist in the List, return -1. index = h1.indexOf(40) print(index) # This should print: 3. In case of element that #doesn't exists in the list this will print -1.

print("/// Test 04 ///")

a2 = [10, 20, 30, 40] h2 = DoublyList(a2) # uses the constructor h2.forwardprint() # This should print: 10,20,30,40.

# inserts containing the given element at the given index. Check validity of index. h2.insert(85,0) h2.forwardprint() # This should print: 85,10,20,30,40. h2.backwardprint() # This should print: 40,30,20,10,85.

print() h2.insert(95,3) h2.forwardprint() # This should print: 85,10,20,95,30,40. h2.backwardprint() # This should print: 40,30,95,20,10,80.

print() h2.insert(75,6) h2.forwardprint() # This should print: 85,10,20,95,30,40,75. h2.backwardprint() # This should print: 75,40,30,95,20,10,85.

print("/// Test 05 ///") a3 = [10, 20, 30, 40, 50, 60, 70] h3 = DoublyList(a3) # uses the constructor h3.forwardprint() # This should print: 10,20,30,40,50,60,70.

# removes at the given index. returns element of the removed node. Check validity of index. return None if index is invalid. print("Removed element: "+ h3.remove(0)) # This should print: Removed element: 10 h3.forwardprint() # This should print: 20,30,40,50,60,70. h3.backwardprint() # This should print: 70,60,50,40,30,20. print("Removed element: "+ h3.remove(3)) # This should print: Removed element: 50 h3.forwardprint() # This should print: 20,30,40,60,70. h3.backwardprint() # This should print: 70,60,40,30,20. print("Removed element: "+ h3.remove(4)) # This should print: Removed element: 70 h3.forwardprint() # This should print: 20,30,40,60. h3.backwardprint() # This should print: 60,40,30,20.