Frequently Used Algo

 1 class Solution {
 2 public:
 3     ListNode* reverseList(ListNode* head) {
 4         ListNode* prev = NULL;
 5         while (head != NULL) {
 6             ListNode* next = head->next;
 7             head->next = prev;
 8             prev = head;
 9             head = next;
10         }
11         return prev;
12     }
13 };