leetcode--Remove Nth Node From End of List

Given a linked list, remove the n^th 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; } * } */public class Solution {    public ListNode removeNthFromEnd(ListNode head, int n) {        ListNode p = head;        while(n>0 && p!=null){            p = p.next;            n--;        }                        ListNode newHead = new ListNode(1);        newHead.next = head;        ListNode q = newHead;               while(p!=null){        q = q.next;        p = p.next;        }                   q.next = q.next.next;        return newHead.next;    }}