19. 删除链表的倒数第 N 个结点

public class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        if(n == 0){
            return head;
        }
        int size = 0;
        ListNode cur = head;
        while (cur != null) {
            size++;
            cur = cur.next;
        }
        ListNode dummyHead = new ListNode();
        dummyHead.next = head;
        ListNode prev = dummyHead;
        for (int i = 0; i < size - n; i++) {
            prev = prev.next;
        }
        prev.next = prev.next.next;
        return dummyHead.next;
    }
}