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 {
    /**
     * 
     * @param head ListNode类 
     * @param n int整型 
     * @return ListNode类
     */
    public ListNode removeNthFromEnd (ListNode head, int n) {
        // write code here
        ListNode fast = head, slow = head;
        // 1→2→3→4→5
        for(int i = 0 ; i < n; i++){
            fast = fast.next;
        }
        //     ↓
        // 1→2→3→4→5
        // ↑

        if(fast == null){ return head.next;}
        while(fast.next != null){
            slow = slow.next;
            fast = fast.next;
        }
        //     ↓ ↓ ↓
        // 1→2→3→4→5
        // ↑ ↑ ↑

        slow.next = slow.next.next;
        return head;

    }
}