LeetCode

Q：
Reverse a singly linked list.
Hint:
A linked list can be reversed either iteratively or recursively. Could you implement both?

A：

# Definition for singly-linked list.class ListNode(object):    def __init__(self, x):        self.val = x        self.next = Noneclass Solution(object):    def reverseList(self, head):        """        :type head: ListNode        :rtype: ListNode        """        pre = None        while head:            current = head            head = head.next            current.next = pre            pre = current        return pre