每日编程-20170509

题目描述
输入一个链表，反转链表后，输出链表的所有元素。

解答：关键是要保存表头

 1 /*
 2 struct ListNode {
 3     int val;
 4     struct ListNode *next;
 5     ListNode(int x) :
 6             val(x), next(NULL) {
 7     }
 8 };*/
 9 class Solution {
10 public:    
11     ListNode* ReverseList(ListNode* pHead) {
12         if(pHead == NULL||pHead->next == NULL) return pHead;
13         ListNode *First = pHead->next->next,*Sec = pHead->next,*Trd = pHead;
14         while(First!=NULL){
15             Sec->next = Trd;
16             Trd = Sec;
17             Sec = First;
18             First = First->next;
19         }
20         Sec->next = Trd;
21         Trd = Sec;
22         pHead->next = NULL;
23         return Sec;
24     }
25 };