p19

 

 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class  {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        ListNode start = new ListNode(0);
		start.next = head;

		ListNode fast = start;
		ListNode slow = start;
		for (int i = 0; i < n + 1; i++) {
			fast = fast.next;
		}
		while (fast != null) {
			fast = fast.next;
			slow = slow.next;
		}
		slow.next = slow.next.next;

		return start.next;
    }
}