反转链表（ LeetCode 206 ）

https://leetcode.cn/problems/reverse-linked-list/

class Solution {
    public ListNode reverseList(ListNode head) {
        if(head==null||head.next==null)
        {
            return head;
        }
        ListNode cur=reverseList(head.next);

        head.next.next=head;
        head.next=null;
        return cur;
    }
}

class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if(head==NULL||head->next==NULL)
        {
            return head;
        }
        ListNode *cur=reverseList(head->next);

        head->next->next=head;
        head->next=nullptr;
        return cur;

    }
};

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if(head==None or head.next==None):
            return head;
        cur=self.reverseList(head.next)

        head.next.next=head
        head.next=None
        return cur