leetcode Reverse Linked List

Description

/**
* 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) {
ListNode *A = head, *B = NULL;
while (head) {
ListNode *ret = head;
head = head->next;
A->next = B;
B = ret;
A = head;
}
return B;
}
};