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) {
        ListNode temp = head;
        int count = 0;
        int number = 0;
        while (temp != null) {
            count += 1;
            temp = temp.next;
        }
        if (n == count) {
            return head.next;
        }
        temp = head;
        ListNode preNode = temp;
        while (temp != null) {
            if (number == count - n) {
                preNode.next = temp.next;
                return head;
            }
            number += 1;
            preNode = temp;
            temp = temp.next;
        }
        return null;
    }
}