Remove Nth Node From End of List

题目连接：http://www.leetcode.com/onlinejudge

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.

public class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
// Start typing your Java solution below
// DO NOT write main() function

if(head == null) return null;

int i = 0;
ListNode phead = head;
ListNode prevhead = head;

while(i++ < n)
{
phead = phead.next;
}

while(phead != null && phead.next != null)
{
head = head.next;
phead = phead.next;
}

if(phead == null) return prevhead.next;
head.next = head.next.next;

return prevhead;
}
}