19. 删除链表的倒数第 N 个结点

谁践踏了优雅 2022-09-08 00:18 98阅读 0赞

[https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/][https_leetcode-cn.com_problems_remove-nth-node-from-end-of-list]

难度中等1519

给你一个链表，删除链表的倒数第 `n`* *个结点，并且返回链表的头结点。

**进阶：**你能尝试使用一趟扫描实现吗？

**示例 1：**

![f9eb7e37e98bfb00965185a6095fcd8d.png][]

输入：head = [1,2,3,4,5], n = 2
    输出：[1,2,3,5]

**示例 2：**

输入：head = [1], n = 1
    输出：[]

**示例 3：**

输入：head = [1,2], n = 1
    输出：[1]

**提示：**

*  链表中结点的数目为 `sz`
 *  `1 <= sz <= 30`
 *  `0 <= Node.val <= 100`
 *  `1 <= n <= sz`

通过次数479,807提交次数1,122,789

/**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode() {}
     *     ListNode(int val) { this.val = val; }
     *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
     * }
     */
    class Solution {
        public ListNode removeNthFromEnd(ListNode head, int n) {
            ListNode tail = head;
            int num =0;
            //链表计数
            while(tail.next!=null)
            {
                tail = tail.next;
                num++;
            }
            if(n == num+1) return head = head.next;
            num = num-n;
            tail = head;
            while(num>0)
            {
                num--;
                tail = tail.next;
            }
            tail.next = tail.next.next;
            return head;
        }
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16][]

/**
     * Definition for singly-linked list.
     * public class ListNode {
     *     int val;
     *     ListNode next;
     *     ListNode() {}
     *     ListNode(int val) { this.val = val; }
     *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
     * }
     */
    class Solution {
        public ListNode removeNthFromEnd(ListNode head, int n) {
            ListNode head1 = new ListNode(0,head);
            ListNode first = head1;
            ListNode seconde = head1;
            while(first.next!=null)
            {
                first = first.next;
                n--;
                if(n<0) seconde = seconde.next; 
            }
            seconde.next = seconde.next.next;
            return head1.next;
        }
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16 1][]

[https_leetcode-cn.com_problems_remove-nth-node-from-end-of-list]: https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/
[f9eb7e37e98bfb00965185a6095fcd8d.png]: /images/20220829/c0445f1c02c64e25886c82a63ba63344.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_Q1NETiBA5Yqq5Yqb5a2m5Lmg55qE5qKF5a2Q_size_18_color_FFFFFF_t_70_g_se_x_16 1]: /images/20220829/768a517a8326448c8b887196590a52eb.png