题解 | #删除链表的倒数第n个节点#

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    public ListNode removeNthFromEnd (ListNode head, int n) {
        if (head == null) {
            return null;
        }

        Stack<ListNode> st = new Stack<>();
        ListNode tmp = head;
        do {
            st.push(tmp);
            tmp = tmp.next;
        } while (tmp != null);

        for (int i = 0; i < n; i++) {
            tmp = st.pop();
        }

        if (st.empty()) {
            return tmp.next;
        }

        ListNode lastNode = st.pop();
        lastNode.next = tmp.next;

        return head;
    }
}