Reverse a singly linked list.
思路：
to slove this problem, I choose a recurrent method, to reverse linked-list nodes one-by-one.
first, point head to NULL.(make the head be a tail)
and then, point cur node to prev node, and then, move prev pointer to cur node, move cur pointer to next node.
until next node move to NULL.
*recursive(递归)，recurrent(递推)
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 if (head == NULL || head->next == NULL) { 13 return head; 14 } 15 ListNode *prev = head, *cur = head->next, *next = cur->next; 16 head->next = NULL; 17 while (next != NULL) { 18 cur->next = prev; 19 prev = cur; 20 cur = next; 21 next = next->next; 22 } 23 cur->next = prev; 24 return cur; 25 } 26 };
原文：http://www.cnblogs.com/huj690/p/4562257.html