Python Program For Making Middle Node Head In A Linked List

# Python3 program to make middle node
# as head of Linked list

# Linked List node
class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

# function to get the middle node
# set it as the beginning of the 
# linked list
def setMiddleHead(head):
    if(head == None):
        return None

    # To traverse nodes 
    # one by one
    one_node = head

    # To traverse nodes by 
    # skipping one
    two_node = head

    # To keep track of previous middle
    prev = None

    while(two_node != None and
          two_node.next != None):

        # For previous node of middle node
        prev = one_node

        # Move one node each time
        one_node = one_node.next

        # Move two nodes each time
        two_node = two_node.next.next

    # Set middle node at head
    prev.next = prev.next.next
    one_node.next = head
    head = one_node

    # Return the modified head
    return head

def push(head, new_data):

    # Allocate new node
    new_node = Node(new_data)

    #Link the old list to new node
    new_node.next = head

    # Move the head to point the new node
    head = new_node

    # Return the modified head
    return head

# A function to print a given linked list
def printList(head):
    temp = head
    while (temp!=None):
        
        print(str(temp.data), end = " ")
        temp = temp.next
    print("")

# Create a list of 5 nodes
head = None
for i in range(5, 0, -1):
    head = push(head, i)

print(" list before: ", end = "")
printList(head)

head = setMiddleHead(head)

print(" list After: ", end = "")
printList(head)
# This code is contributed by Pranav Devarakonda