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
     *
     *
     * @param pHead ListNode类
     * @param k int整型
     * @return ListNode类
     */
    public ListNode FindKthToTail (ListNode pHead, int k) {
        ListNode fast = pHead;
        ListNode slow = pHead;

        for (int i = 0; i < k && fast != null; i++) {
            fast = fast.next;
		    // 这里是越界了
            if (fast == null && i < k - 1) {
                return null;
            }
        }
	  
        while (fast != null) {
            fast = fast.next;
            slow = slow.next;
        }

        return slow;
    }
}