leetcode Remove Nth Node From End of List(Java)

题目链接：点击打开链接

类型：Remove Nth Node From End of List

解法：

/**
* 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 before = head;
int len = 0;
while (before != null)
{
before = before.next;
len++;
}

if (len == n)
return head.next;
if (len == 2)
{
if (n == 2)
return head.next;
else
{
ListNode s = new ListNode(head.val);
s.next = null;
}
}

before = head;
int j = 1;
while(j < len-n)
{
before = before.next;
j++;
}

ListNode temp = before.next.next;
before.next = temp;

return head;
}
}