【python】leetcode206. 反转链表

【详解Leetcode_206】反转链表 Reverse Linked List

题目链接：206. 反转链表

class Solution:
    def reverseList(self, head): #head = [1,2,3],1->2->3->null
     #   法1
    #     if head == None or head.next == None:
    #         return head
        
    #     last = self.reverseList(head.next)
    #     head.next.next = head
    #     head.next = None
    #     return last

#法2
        pre = None;
        cur = head;next = None
        while cur != None:
            nxt = cur.next   #cur = 1，nxt记录2
            cur.next = pre   #1的下一个元素指向前面的元素null,修改第一个箭头->改为<-
            pre = cur   # 移动pre到1
            cur = nxt   # cur指向2
        return pre