递归版
/**
* 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 || !head->next) {
return head;
}
ListNode*p = reverseList(head->next);
head ->next->next = head;
head ->next = NULL;
return p;
}
};