链表中倒数第k个结点（牛客）《数据结构入门到精通N6》

struct ListNode* FindKthToTail(struct ListNode* pListHead, int k ) {
    // write code here
    if(pListHead==NULL)
        return NULL;
    struct ListNode* slow=pListHead;
    struct ListNode* fast=pListHead;
    while(k--)
    {
        if(fast)
        {
            fast=fast->next;
        }
        else
        {
            return NULL;
        }
    }
    while(fast!=NULL)
    {
        slow=slow->next;
        fast=fast->next;
    }
    return slow;
}