Python. faster than 95.06%. O(n), Super simple & clear solution.
\tclass Solution:\n\t\tdef reorderList(self, head: ListNode) -> None:\n\t\t\tif not head: return head\n\t\t\tslow, fast = head, head\n\t\t\twhile fast.next and 
\tclass Solution:\n\t\tdef reorderList(self, head: ListNode) -> None:\n\t\t\tif not head: return head\n\t\t\tslow, fast = head, head\n\t\t\twhile fast.next and fast.next.next:\n\t\t\t\tslow = slow.next\n\t\t\t\tfast = fast.next.next\n\t\t\t\n\t\t\tprev, cur = None, slow.next\n\t\t\twhile cur:\n\t\t\t\tsave = cur.next\n\t\t\t\tcur.next = prev\n\t\t\t\tprev = cur\n\t\t\t\tcur = save\n\t\t\tslow.next = None\n\t\t\t\n\t\t\thead2 = prev\n\t\t\twhile head2:\n\t\t\t\tsave1 = head.next\n\t\t\t\thead.next = head2\n\t\t\t\thead = head2\n\t\t\t\thead2 = save1
['Linked List', 'Python', 'Python3']