CODE

/**
* Definition for singly-linked list.
* public class ListNode {
*     public int val;
*     public ListNode next;
*     public ListNode(int val=0, ListNode next=null) {
*         this.val = val;
*         this.next = next;
*     }
* }
*/

public class Solution {
  public ListNode RemoveNthFromEnd(ListNode head, int n) {
    if (head.next == null)
      return null;

    List<ListNode> stack = new List<ListNode>();

    ListNode origHead = head;
    while (head.next != null)
    {
      stack.Insert(0, head);
      head = head.next;
    }

    /* if n = 1, simply remove last node: set prev node's next to null */
    if (n == 1)
    {
      stack[0].next = null;
      return origHead;
    }

    int count = 1;

    while (count < n - 1)
    {
      head = stack[0];
      stack.RemoveAt(0);
      count++;
    }

    stack[0].next = null;
    stack.RemoveAt(0);
    if (stack.Count > 0)
      stack[0].next = head;
    else
      origHead = head;

    return origHead;

  }
}