剑指offer：00倒数第k个节点

/*
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(nullptr == pListHead||k<0){
        return pListHead;
    }
    ListNode* pAhead = pListHead;
    ListNode* pBehind = nullptr;
    for(unsigned int i=0;i<k-1;i++){
        pAhead = pAhead->next;
        if(nullptr==pAhead){
            return nullptr;
        }
    }
    pBehind = pListHead;
    while(pAhead->next!=nullptr){
        pAhead=pAhead->next;
        pBehind=pBehind->next;
    }
    return pBehind;
    }
};