14，链表中倒数第k个结点

遍历链表，存入ArrayList

import java.util.ArrayList;
public class Solution {
    public ListNode FindKthToTail(ListNode head,int k) {
        ArrayList<ListNode> list = new ArrayList<>();
        if(head == null)
            return null;
        ListNode node = head;
        while(node != null){
            list.add(node);
            node = node.next;
        }
        if(k > list.size() || k <= 0)
            return null;

        return list.get(list.size() - k);
    }
}