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 class Solution {

 



    public ListNode removeNthFromEnd (ListNode head, int n) {
         
        // write code here
        //先找到倒数第n个节点
        ListNode f = head;
        ListNode s = head;

        while(n>0){
            if(f!=null){
                f = f.next;
            }//此题不用考虑n大于链表长度
            n--;
                

        }

        ListNode pre = new ListNode(0);
        pre.next = s;

        if(f==null){
            //此时说明删除的是头节点，因为n最多等于链表长度
            return head.next;
        }
       while(f!=null){
        f=f.next;

        s=s.next;
        pre = pre.next;

       }
       pre.next = s.next;

       





        return head;
    }
}