Reverse Linked List

题目：Reverse a singly linked list.

思路：

代码：

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
//还有一种递归的写法。
//https://github.com/JSRGFJZ/leetcode-5/blob/master/algorithms/reverseLinkedList/reverseLinkedList.cpp#L38
ListNode* reverseList(ListNode* head) {
ListNode *tail=NULL;

if(head==NULL)  return head;

while(head!=NULL){
ListNode *tmp=head->next;
head->next=tail;
tail=head;
head=tmp;
}
head=tail;
return head;
}
};