二刷1110

Author: diguage

docs/1110-delete-nodes-and-return-forest.adoc

@@ -1,46 +1,65 @@
 [#1110-delete-nodes-and-return-forest]
-= 1110. Delete Nodes And Return Forest
+= 1110. 删点成林
 
-{leetcode}/problems/delete-nodes-and-return-forest/[LeetCode - Delete Nodes And Return Forest^]
+https://leetcode.cn/problems/delete-nodes-and-return-forest/[LeetCode - 1110. 删点成林 ^]
 
-Given the `root` of a binary tree, each node in the tree has a distinct value.
+给出二叉树的根节点 `root`，树上每个节点都有一个不同的值。
 
-After deleting all nodes with a value in `to_delete`, we are left with a forest (a disjoint union of trees).
+如果节点值在 `to_delete` 中出现，我们就把该节点从树上删去，最后得到一个森林（一些不相交的树构成的集合）。
 
-Return the roots of the trees in the remaining forest.  You may return the result in any order.
+返回森林中的每棵树。你可以按任意顺序组织答案。
 
- 
-*Example 1:*
+*示例 1：*
 
-image::https://assets.leetcode.com/uploads/2019/07/01/screen-shot-2019-07-01-at-53836-pm.png[{image_attr}]
+image::images/1110-01.png[{image_attr}]
+
+....
+输入：root = [1,2,3,4,5,6,7], to_delete = [3,5]
+输出：[[1,2,null,4],[6],[7]]
+....
+
+*示例 2：*
+
+....
+输入：root = [1,2,4,null,3], to_delete = [3]
+输出：[[1,2,4]]
+....
 
-[subs="verbatim,quotes,macros"]
-----
-*Input:* root = [1,2,3,4,5,6,7], to_delete = [3,5]
-*Output:* [[1,2,null,4],[6],[7]]
-----
 
- 
-*Constraints:*
+*提示：*
 
+* 树中的节点数最大为 `1000`。
+* 每个节点都有一个介于 `1` 到 `1000` 之间的值，且各不相同。
+* `+to_delete.length <= 1000+`
+* `to_delete` 包含一些从 `1` 到 `1000`、各不相同的值。
 
-* The number of nodes in the given tree is at most `1000`.
-* Each node has a distinct value between `1` and `1000`.
-* `to_delete.length <= 1000`
-* `to_delete` contains distinct values between `1` and `1000`.
 
 == 思路分析
 
-利用递归，在“后序遍历”阶段，对当前阶段判断是否需要删除。
 
 [[src-1110]]
+[tabs]
+====
+一刷::
++
+--
 [{java_src_attr}]
 ----
 include::{sourcedir}/_1110_DeleteNodesAndReturnForest.java[tag=answer]
 ----
+--
+
+二刷::
++
+--
+[{java_src_attr}]
+----
+include::{sourcedir}/_1110_DeleteNodesAndReturnForest_2.java[tag=answer]
+----
+--
+====
+
 
 == 参考资料
 
-. https://leetcode.cn/problems/delete-nodes-and-return-forest/solutions/2286145/shan-dian-cheng-lin-by-leetcode-solution-gy95/[1110. 删点成林 - 官方题解^]
-. https://leetcode.cn/problems/delete-nodes-and-return-forest/solutions/2289131/he-shi-ji-lu-da-an-pythonjavacgo-by-endl-lpcd/[1110. 删点成林 - 简洁写法！^]
 

docs/images/1110-01.png

@@ -848,6 +848,11 @@ endif::[]
 |{doc_base_url}/1496-path-crossing.adoc[题解]
 |✅ 想找个巧办法，结果失败！还是用记录轨迹的办法搞定了。
 
+|{counter:codes2503}
+|{leetcode_base_url}/delete-nodes-and-return-forest/[1110. 删点成林^]
+|{doc_base_url}/1110-delete-nodes-and-return-forest.adoc[题解]
+|✅ 深度优先遍历，把父节点传到递归参数里，同时标注一下是左子树还是右子树。
+
 |===
 
 截止目前，本轮练习一共完成 {codes2503} 道题。

logbook/202503.adoc

@@ -0,0 +1,46 @@
+package com.diguage.algo.leetcode;
+
+import com.diguage.algo.util.TreeNode;
+
+import java.util.*;
+
+public class _1110_DeleteNodesAndReturnForest_2 {
+  // tag::answer[]
+
+  /**
+   * @author D瓜哥 · https://www.diguage.com
+   * @since 2025-05-27 21:06:27
+   */
+  public List<TreeNode> delNodes(TreeNode root, int[] to_delete) {
+    Set<Integer> set = new HashSet<>(to_delete.length);
+    Arrays.stream(to_delete).forEach(set::add);
+    List<TreeNode> result = new ArrayList<>();
+    dfs(root, set, result, null, true);
+    return result;
+  }
+
+  private void dfs(TreeNode node, Set<Integer> set,
+                   List<TreeNode> result, TreeNode parent, boolean left) {
+    if (node == null) {
+      return;
+    }
+    if (set.contains(node.val)) {
+      if (parent != null) {
+        if (left) {
+          parent.left = null;
+        } else {
+          parent.right = null;
+        }
+      }
+      dfs(node.left, set, result, null, true);
+      dfs(node.right, set, result, null, false);
+    } else {
+      if (parent == null) {
+        result.add(node);
+      }
+      dfs(node.left, set, result, node, true);
+      dfs(node.right, set, result, node, false);
+    }
+  }
+  // end::answer[]
+}