链表中倒数第K个节点，递归，Java

递归返回时需要记录一下返回到倒数第几个节点了

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    int n = 0;
    int i = -1;
    public ListNode FindKthToTail(ListNode head,int k) {
        i ++;
        if(head == null) {
            return null;
        }
        head.next = FindKthToTail(head.next, k);
        n ++;
        if(i < k) {
            return null;
        }
        // 这里是把倒数第K个节点当做头结点返回了
        return n <= k ? head : head.next;
    }
}