struct ListNode* FindKthToTail(struct ListNode* pListHead, int k ) {
    struct ListNode* fast = pListHead;
    struct ListNode* slow = pListHead;
    while(k--)
    {
        if(fast == NULL)
        {
            return NULL;
        }
        fast = fast->next;
    }
    while(fast)
    {
        slow = slow->next;
        fast = fast->next;
    }
    return slow;
}

struct ListNode* middleNode(struct ListNode* head){
    struct ListNode* fast = head;
    struct ListNode* slow = head;
    while(fast && fast->next)
    {
        fast = fast->next->next;
        slow = slow->next;
    }
    return slow;


}