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 tempHead = new ListNode(-1);
        tempHead.next = head;
        ListNode tempNode = tempHead;

        List<ListNode> list = new ArrayList<>();
        while (tempNode != null) {
            list.add(tempNode);
            tempNode = tempNode.next;
        }
        System.out.println("list size"+list.size());
        ListNode lastNode = null;
        ListNode lastLastNode = null;
        //倒数第几
        int num = 0;
        for(int i = list.size()-1; i>= 1; i--){
            num ++;
            lastLastNode = list.get(i);
            if(num == n){
                break;
            }else{
                lastNode = lastLastNode;
            }
        }

        tempNode = list.get(0);
        tempHead = tempNode;
        for(int j = 1; j<list.size() - n; j++){
            ListNode node = list.get(j);
            tempNode.next = node;
            tempNode = tempNode.next;
        }
        tempNode.next = lastNode;
        return tempHead.next;
    }
}