Leetcode 876. Middle of the Linked List

Problem statement :

Given the head of a singly linked list, return the middle node of the linked list.

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

Examples :

Example 1:

Input: head = [1,2,3,4,5]
Output: [3,4,5]
Explanation: The middle node of the list is node 3.

Example 2:

Input: head = [1,2,3,4,5,6]
Output: [4,5,6]
Explanation: Since the list has two middle nodes with values 3 and 4, we return the second one.

Constraints:

The number of nodes in the list is in the range [1, 100]. 1 <= Node.val <= 100

Solution :

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def middleNode(self, head: Optional[ListNode]) -> Optional[ListNode]:
        slow = head
        fast = head 
        while fast is not None and fast.next is not None:
            slow = slow.next
            fast = fast.next.next
        return slow