Remove Nth Node From End of List

Given a linked list, remove the nth node from the end of list and return its head.

For example,

   Given linked list: 1->2->3->4->5, and n = 2.

   After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:
Given n will always be valid.
Try to do this in one pass.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode newList = new ListNode(0);   //头结点
        newList.next = head;
        ListNode tmp =head;
        ListNode pre = newList;
        int i = n;
        while (i>1){
            head = head.next;
            i--;
        }
        while (head.next!=null){
            head = head.next;
            pre = pre.next;
        }
        pre.next = pre.next.next;
        return newList.next;
    }
}