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

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
            val(x), next(NULL) {
    }
};*/
class Solution {
public:    
    ListNode* ReverseList(ListNode* pHead) {
        if(pHead == NULL||pHead->next == NULL) return pHead;
        ListNode *First = pHead->next->next,*Sec = pHead->next,*Trd = pHead;
        while(First!=NULL){
            Sec->next = Trd;
            Trd = Sec;
            Sec = First;
            First = First->next;
        }
        Sec->next = Trd;
        Trd = Sec;
        pHead->next = NULL;
        return Sec;
    }
};