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Python Program to Print the Alternate Nodes in a Linked List using Recursion
When it is required to print the alternate nodes in a linked list using recursion, a method to add elements to the linked list, a method to display the elements of the linked list, and a method to get the alternate values of a linked list are defined. Another helper function is used that calls the previously defined method to get alternate values.
Below is a demonstration for the same −
Example
class Node:
def __init__(self, data):
self.data = data
self.next = None
class my_linked_list:
def __init__(self):
self.head = None
self.last_node = None
def add_value(self, my_data):
if self.last_node is None:
self.head = Node(my_data)
self.last_node = self.head
else:
self.last_node.next = Node(my_data)
self.last_node = self.last_node.next
def print_it(self):
curr = self.head
while curr:
print(curr.data)
curr = curr.next
def alternate_nodes(self):
self.alternate_helper_fun(self.head)
def alternate_helper_fun(self, curr):
if curr is None:
return
print(curr.data, end = ' ')
if curr.next:
self.alternate_helper_fun(curr.next.next)
my_instance = my_linked_list()
my_list = input("Enter the elements of the linked list :").split()
for elem in my_list:
my_instance.add_value(elem)
print("The alternate elements in the linked list are :")
my_instance.alternate_nodes()Output
Enter the elements of the linked list :78 56 34 52 71 96 0 80 The alternate elements in the linked list are : 78 34 71 0
Explanation
The ‘Node’ class is created.
Another ‘my_linked_list’ class with required attributes is created.
It has an ‘init’ function that is used to initialize the first element, i.e the ‘head’ to ‘None’ and last node to ‘None’.
Another method named ‘add_value’ is defined, that is used to add data to the linked list.
Another method named ‘print_it’ is defined, that iterates over the list, and prints the elements.
Another method named ‘alternate_nodes’ is defined that is used to call the helper function.
Another helper function, named ‘alternate_helper_fun’ is defined that is used to iterate through the linked list, and display elements in alternative indices.
It is a recursive function, hence it calls itself again and again.
This is used to call the ‘alternate_nodes’ function since recursion is being used.
An object of the ‘my_linked_list’ class is created.
The alternate_nodes method is called, to display the alternate elements.
This output is displayed on the console.
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