题解 | #链表中倒数最后k个结点#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可 吴师兄
     * 这个使用双指针思路非常的巧妙
     * 
     * @param pHead ListNode类 
     * @param k int整型 
     * @return ListNode类
     */
    public ListNode FindKthToTail (ListNode pHead, int k) {
        
        ListNode before = pHead;
        ListNode after = pHead;

        for(int i =0 ;i < k; i++) {
            if(after == null) {return null;}
            after = after.next;
        }

        while(after != null) {
            after = after.next;
            before = before.next;
        }

        return before;
    }
}