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;

    }
};