Problem Solution # Definition for singly-linked list. # class ListNode: # def __init__(self, val=0, next=None): # self.val = val # self.next = next class Solution: def sortList(self, head: Optional[ListNode]) -> Optional[ListNode]: if not head or not head.next: return head # find the middle of the linked list # https://leetcode.com/problems/middle-of-the-linked-list/ slow = head fast = head.next..