Python Program To Merge A Linked List Into Another Linked List At Alternate Positions

# Python program to merge a linked list 
# into another at alternate positions
class Node(object):
    def __init__(self, data:int):
        self.data = data
        self.next = None

class LinkedList(object):
    def __init__(self):
        self.head = None
        
    def push(self, new_data:int):
        new_node = Node(new_data)
        new_node.next = self.head

        # 4. Move the head to point to 
        # new Node
        self.head = new_node
        
    # Function to print linked list from 
    # the Head
    def printList(self):
        temp = self.head
        while temp != None:
            print(temp.data)
            temp = temp.next
            
    # Main function that inserts nodes of linked 
    # list q into p at alternate positions. 
    # Since head of first list never changes
    # but head of second list/ may change, 
    # we need single pointer for first list and 
    # double pointer for second list.
    def merge(self, p, q):
        p_curr = p.head
        q_curr = q.head

        # swap their positions until one 
        # finishes off
        while p_curr != None and q_curr != None:

            # Save next pointers
            p_next = p_curr.next
            q_next = q_curr.next

            # make q_curr as next of p_curr
            # change next pointer of q_curr
            q_curr.next = p_next  

            # change next pointer of p_curr
            p_curr.next = q_curr  

            # update current pointers for next 
            # iteration
            p_curr = p_next
            q_curr = q_next
            q.head = q_curr

# Driver code
llist1 = LinkedList()
llist2 = LinkedList()

# Creating Linked lists
# 1.
llist1.push(3)
llist1.push(2)
llist1.push(1)
llist1.push(0)

# 2.
for i in range(8, 3, -1):
    llist2.push(i)

print("First Linked List:")
llist1.printList()

print("Second Linked List:")
llist2.printList()

# Merging the LLs
llist1.merge(p=llist1, q=llist2)

print("Modified first linked list:")
llist1.printList()

print("Modified second linked list:")
llist2.printList()

# This code is contributed by Deepanshu Mehta