/
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode next;
* ListNode(int x) : val(x), next(NULL) {}
* };
/
class Solution {
public:
ListNode reverseList(ListNode head) {
if(head==NULL)return NULL;
auto a=head,b=a->next;
while(b){
auto c=b->next;
b->next=a;
a=b;
b=c;
}
head->next=NULL;
return a;
}
};