Python Program For Finding The Middle Element Of A Given Linked List

# Python3 program to find middle of 
# the linked list
# Node class 
class Node: 
  
    # Function to initialise the 
    # node object 
    def __init__(self, data): 
   
        # Assign data 
        self.data = data 

        # Initialize next as null  
        self.next = None  
  
# Linked List class contains a 
# Node object 
class LinkedList: 
  
    # Function to initialize head 
    def __init__(self): 
        self.head = None

    # Function to insert a new node at 
    # the beginning  
    def push(self, new_data):  
        new_node = Node(new_data)  
        new_node.next = self.head  
        self.head = new_node

    # Print the linked list
    def printList(self):
        node = self.head
        while node:
            print(str(node.data) + 
                  "->", end = "")
            node = node.next
        print("NULL")

    # Function that returns middle.
    def printMiddle(self):

        # Initialize two pointers, one will go 
        # one step a time (slow), another two 
        # at a time (fast)
        slow = self.head
        fast = self.head

        # Iterate till fast's next is null (fast 
        # reaches end)
        while fast and fast.next:
            slow = slow.next
            fast = fast.next.next
        
        # Return the slow's data, which would be 
        # the middle element.
        print("The middle element is ", slow.data)

# Driver code
if __name__=='__main__': 
  
    # Start with the empty list 
    llist = LinkedList() 
  
    for i in range(5, 0, -1):
        llist.push(i)
        llist.printList()
        llist.printMiddle()

# This code is contributed by Kumar Shivam (kshivi99)

# Python program to implement
# the above approach

# Node class 
class Node: 
   
    # Function to initialise the 
    # node object 
    def __init__(self, data):

        # Assign data  
        self.data = data  

        # Initialize next as null 
        self.next = None  
   
# Linked List class contains a 
# Node object 
class LinkedList: 
   
    # Function to initialize head 
    def __init__(self): 
        self.head = None
 
    # Function to insert a new node at 
    # the beginning  
    def push(self, new_data):  
        new_node = Node(new_data)  
        new_node.next = self.head  
        self.head = new_node
 
    # Print the linked list
    def printList(self):
        node = self.head
        while node:
            print(str(node.data) + 
                      "->", end = "")
            node = node.next
        print("NULL")
 
    # Function to get the middle of
    #  the linked list
    def printMiddle(self):
        count = 0
        mid = self.head
        heads = self.head
  
        while(heads != None):
      
        # Update mid, when 'count'
        # is odd number 
            if count & 1:
                mid = mid.next
            count += 1
            heads = heads.next
            
        # If empty list is provided 
        if mid != None:
            print("The middle element is ", 
                   mid.data)
 
# Driver code
if __name__=='__main__': 
   
    # Start with the empty list 
    llist = LinkedList() 
   
    for i in range(5, 0, -1):
        llist.push(i)
        llist.printList()
        llist.printMiddle()
 
 # This code is contributed by Manisha_Ediga