Java实现-链表的倒数第n个节点

找到单链表倒数第n个节点，保证链表中节点的最少数量为n。

您在真实的面试中是否遇到过这个题？ 

Yes

样例

给出链表 3->2->1->5->null和n = 2，返回倒数第二个节点的值1.

/** * Definition for ListNode. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int val) { *         this.val = val; *         this.next = null; *     } * } */ public class Solution {    /**     * @param head: The first node of linked list.     * @param n: An integer.     * @return: Nth to last node of a singly linked list.      */    ListNode nthToLast(ListNode head, int n) {        // write your code here        if(head==null)return head;int count=0;ListNode node=head;while(node!=null){node=node.next;count++;}if(n>count)return null;ListNode dummy=new ListNode(0);dummy.next=head;ListNode node1=dummy;ListNode node2=dummy;int i=0;while(i<=n&&node1!=null){i++;node1=node1.next;}while(node1!=null){node1=node1.next;node2=node2.next;}node2=node2.next;return node2;    }}