/*

struct ListNode {

	int val;

	struct ListNode *next;

	ListNode(int x) :

			val(x), next(NULL) {

	}

};*/

class Solution {

public:

    ListNode* ReverseList(ListNode* pHead) {

        if(pHead == nullptr)

        {

            return nullptr;

        }

        ListNode *pNode = pHead;

        ListNode *pPrev = nullptr;

        ListNode *pRet = nullptr;

        while(pNode != nullptr)

        {

            ListNode *pNext = pNode->next;

            if(pNext == nullptr)

            {

                pRet = pNode;

            }

            pNode->next = pPrev; //精髓

            pPrev = pNode;

            pNode = pNext;

        }

        return pRet;

    }

};