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 dummy = new ListNode(-1);
        dummy.next = head;
        ListNode p1 = dummy;
        ListNode p2 = dummy;
        for(int i = 0;i <= n;i++){
            if(p2 != null){
                p2 = p2.next;
            }else return null;
        }
        while(p2 != null){
            p1 = p1.next;
            p2 = p2.next;
        }
        
        if(p1.next != null) p1.next = p1.next.next;
        else p1 = null;
        return dummy.next;
    }
}