876.middle of the linked list

Given a non-empty, singly linked list with head node head, return a middle node of linked list.

If there are two middle nodes, return the second middle node.

Input: [1,2,3,4,5]
Output: Node 3 from this list (Serialization: [3,4,5])
The returned node has value 3.  (The judge's serialization of this node is [3,4,5]).
Note that we returned a ListNode object ans, such that:
ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.

Input: [1,2,3,4,5,6]
Output: Node 4 from this list (Serialization: [4,5,6])
Since the list has two middle nodes with values 3 and 4, we return the second one.

• The number of nodes in the given list will be between 1 and 100.

1. updating

Definition for singly-linked list.
class ListNode:
   def __init__(self, x):
       self.val = x
       self.next = None

class Solution:
def middleNode(self, head):
    a=head
    b=head
    b=b.next
    while(b!=None):
        a=a.next
        b=b.next
        if(b!=None):
            b=b.next
    return a