剑指offer：链表中倒数第k个结点

/*struct ListNode {    int val;    struct ListNode *next;    ListNode(int x) :            val(x), next(NULL) {    }};*/class Solution {public:    ListNode* FindKthToTail(ListNode* pListHead, unsigned int k) {        if(pListHead==NULL||k==0) return NULL;        ListNode *p=pListHead,*r=pListHead;        for(unsigned int n=1;n!=k;++n) {            p=p->next;        if(p==NULL) return NULL;        }        while(p->next!=NULL){            r=r->next;            p=p->next;        }        return r;    }};