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 cur = head;
        int count = 0;

        while (cur != null) {
            count++;
            cur = cur.next;
        }

        if (n - count > 0) {
            return head;
        }

        int i = 0;

        ListNode preHead = new ListNode(-1);
        preHead.next = head;
        cur = preHead;

        while (i < count - n) { // 找到删除节点的前驱节点
            i++;
            cur = cur.next;
        }

        cur.next = cur.next.next;// 删除

        return preHead.next;
    }
}