链表的反转

微信图片_20191221163851.jpg

class Solution:
    # 返回ListNode
    def ReverseList(self, pHead):
        # write code here
        if pHead is None:
            return None
        if pHead.next is None:
            return pHead
        pre = pHead
        cur = pHead.next
        last = pHead.next.next
        pre.next = None
        
        while last != None:
            cur.next = pre
            pre = cur
            cur = last
            last = last.next
        cur.next = pre
        return cur