二刷19

Author: diguage

docs/0019-remove-nth-node-from-end-of-list.adoc

@@ -1,38 +1,72 @@
 [#0019-remove-nth-node-from-end-of-list]
-= 19. Remove Nth Node From End of List
+= 19. 删除链表的倒数第 N 个结点
 
-{leetcode}/problems/remove-nth-node-from-end-of-list/[LeetCode - Remove Nth Node From End of List^]
+https://leetcode.cn/problems/remove-nth-node-from-end-of-list/[LeetCode - 19. 删除链表的倒数第 N 个结点 ^]
 
-Given a linked list, remove the _n_-th node from the end of list and return its head.
+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。
 
-*Example:*
+*示例 1：*
 
-[subs="verbatim,quotes,macros"]
-----
-Given linked list: *1->2->3->4->5*, and *_n_ = 2*.
+image::images/0019-01.jpg[{image_attr}]
 
-After removing the second node from the end, the linked list becomes *1->2->3->5*.
-----
+....
+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]
+....
 
-*Note:*
 
-Given _n_ will always be valid.
+*提示：*
 
-*Follow up:*
+* 链表中结点的数目为 `sz`
+* `+1 <= sz <= 30+`
+* `+0 <= Node.val <= 100+`
+* `+1 <= n <= sz+`
 
-Could you do this in one pass?
+**进阶：**你能尝试使用一趟扫描实现吗？
 
-== 解题分析
+
+== 思路分析
 
 快慢指针
 
-image::images/0019-0.png[{image_attr}]
+image::images/0019-02.png[{image_attr}]
 
 [[src-0019]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_0019_RemoveNthNodeFromEndOfList.java[tag=answer]
 ----
+--
+
+二刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_0019_RemoveNthNodeFromEndOfList_2.java[tag=answer]
+----
+--
+====
+
 
 == 参考资料
 

docs/images/0019-01.jpg

@@ -255,6 +255,11 @@ endif::[]
 |{doc_base_url}/0142-linked-list-cycle-ii.adoc[题解]
 |✅ 双指针+数学
 
+|{counter:codes2503}
+|{leetcode_base_url}/remove-nth-node-from-end-of-list/[19. 删除链表的倒数第 N 个结点^]
+|{doc_base_url}/0019-remove-nth-node-from-end-of-list.adoc[题解]
+|✅ 双指针+虚拟头节点。使用虚拟头结点会省事好多。
+
 |===
 ˚
 截止目前，本轮练习一共完成 {codes2503} 道题。

docs/images/0019-0.png renamed to docs/images/0019-02.png

@@ -36,6 +36,9 @@ public class _0019_RemoveNthNodeFromEndOfList {
      * Runtime: 0 ms, faster than 100.00% of Java online submissions for Remove Nth Node From End of List.
      *
      * Memory Usage: 34.6 MB, less than 100.00% of Java online submissions for Remove Nth Node From End of List.
+     *
+     * @author D瓜哥 · https://www.diguage.com
+     * @since 2019-07-26 20:17
      */
     public ListNode removeNthFromEnd(ListNode head, int n) {
         if (Objects.isNull(head) || n == 0) {

logbook/202503.adoc

@@ -0,0 +1,38 @@
+package com.diguage.algo.leetcode;
+
+import com.diguage.algo.util.ListNode;
+import com.diguage.util.ListNodes;
+
+import java.util.Arrays;
+
+public class _0019_RemoveNthNodeFromEndOfList_2 {
+  // tag::answer[]
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-04-15 21:26:08
+   */
+  public ListNode removeNthFromEnd(ListNode head, int n) {
+    ListNode dummy = new ListNode(0);
+    dummy.next = head;
+    ListNode fast = dummy;
+    while (n >= 0) {
+      fast = fast.next;
+      n--;
+    }
+    ListNode pre = dummy;
+    ListNode slow = head;
+    while (fast != null) {
+      fast = fast.next;
+      pre = slow;
+      slow = slow.next;
+    }
+    pre.next = slow.next;
+    return dummy.next;
+  }
+  // end::answer[]
+
+  public static void main(String[] args) {
+    new _0019_RemoveNthNodeFromEndOfList_2()
+      .removeNthFromEnd(ListNodes.build(Arrays.asList(1)), 1);
+  }
+}