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 {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类
     * @param n int整型
     * @return ListNode类
     */
    public ListNode removeNthFromEnd (ListNode head, int n) {
        // write code here

        ListNode reverNode = getReverseNode(head);

        int m = 0;
        ListNode cur = reverNode;

        if (n == 1) {
            cur = reverNode.next;
        } else {
            while (reverNode != null) {
                m++;
                if (m == n - 1) {
                    ListNode temp = reverNode.next;
                    reverNode.next = temp.next;
                    break;

                } else {
                    reverNode = reverNode.next;
                }
            }
        }

        return getReverseNode(cur);
    }

    public ListNode getReverseNode(ListNode head) {

        ListNode pre = null;

        while (head != null) {
            ListNode next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }
}