java实现输入一个链表，输出该链表中倒数第k个结点。

package com.pomay.offer;

/**
* 输入一个链表，输出该链表中倒数第k个结点。
*
* @author pomay
*
*/
class ListNode {
int val;
ListNode next = null;

ListNode(int val) {
this.val = val;
}
}

public class Solution_lianbiaofindK {
public ListNode FindKthToTail(ListNode head, int k) {
if (head == null || k < 0) {
return null;
}
ListNode last = head;
for (int i = 1; i < k; i++) {
if (head.next != null) {
head = head.next;
} else
return null;
}
while (head.next != null) {
head = head.next;
last = last.next;
}
return last;

}

public static void main(String[] args) {
ListNode head = new ListNode(1);
head.next = new ListNode(2);
head.next.next = new ListNode(3);
head.next.next.next = new ListNode(6);
int k = 4;
Solution_lianbiaofindK s = new Solution_lianbiaofindK();
ListNode last = s.FindKthToTail(head, k);
System.out.println(last.val);
}

}