题目描述

输入一个链表，反转链表后，输出新链表的表头。
/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
            val(x), next(NULL) {
    }
};*/
class Solution {
public:
    ListNode* ReverseList(ListNode* pHead) {
        auto pre = pHead;
        auto back = pHead;

        while(back != nullptr && back->next != nullptr) {
            pre = back->next;
            back->next = pre->next;
            pre->next = pHead;
            pHead = pre;
        }
        return pHead;
    }
};