reverse linked list

rev_linked_list.py

#
# Recursively change each node of the linked list such that next
# is the last node seen during a linear scan of the linked list.
#
class Solution:
    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
        def go(node = head, last = None):
            next = node.next
            node.next = last
            if not next:
                return node
            return go(next, node)
        return go() if head else None