【剑指offer】反转链表

/*
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 *root=ReverseList(pHead->next);

    pHead->next->next=pHead;
    pHead->next=NULL;

    return root;
}
};