19. Remove Nth Node From End of List

class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        // d -> 1 -> 2 -> 3 -> 4 -> 5, n = 2
        //                f
        // s
        ListNode dummyHead = new ListNode(-1, head);
        ListNode first = head, second = dummyHead;
        for (int i = 0; i < n; i++) {
            first = first.next;
        }
        while (first != null) {
            first = first.next;
            second = second.next;
        }

        second.next = second.next.next;
        return dummyHead.next;
    }
}

Reference

19. Remove Nth Node From End of List
剑指 Offer II 021. 删除链表的倒数第 n 个结点