1 /** 2  * Definition for singly-linked list. 3  * struct ListNode { 4  *     int val; 5  *     ListNode *next; 6  *     ListNode(int x) : val(x), next(NULL) {} 7  * }; 8  */ 9 class Solution {10 public:11     ListNode* reverseList(ListNode* head) {12         ListNode* pre = NULL;13         ListNode* cur = head;14         while(cur != NULL)15         {16             ListNode* temp = cur->next;17             cur->next = pre;18             pre = cur;19             cur = temp;20         }21         return pre;22     }23 };