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Author: NinePiece2

Solutions/0608-tree-node/README.md

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+<p>Table: <code>Tree</code></p>
+
+<pre>
++-------------+------+
+| Column Name | Type |
++-------------+------+
+| id          | int  |
+| p_id        | int  |
++-------------+------+
+id is the column with unique values for this table.
+Each row of this table contains information about the id of a node and the id of its parent node in a tree.
+The given structure is always a valid tree.
+</pre>
+
+<p>&nbsp;</p>
+
+<p>Each node in the tree can be one of three types:</p>
+
+<ul>
+	<li><strong>&quot;Leaf&quot;</strong>: if the node is a leaf node.</li>
+	<li><strong>&quot;Root&quot;</strong>: if the node is the root of the tree.</li>
+	<li><strong>&quot;Inner&quot;</strong>: If the node is neither a leaf node nor a root node.</li>
+</ul>
+
+<p>Write a solution to report the type of each node in the tree.</p>
+
+<p>Return the result table in <strong>any order</strong>.</p>
+
+<p>The result format is in the following example.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/10/22/tree1.jpg" style="width: 304px; height: 224px;" />
+<pre>
+<strong>Input:</strong> 
+Tree table:
++----+------+
+| id | p_id |
++----+------+
+| 1  | null |
+| 2  | 1    |
+| 3  | 1    |
+| 4  | 2    |
+| 5  | 2    |
++----+------+
+<strong>Output:</strong> 
++----+-------+
+| id | type  |
++----+-------+
+| 1  | Root  |
+| 2  | Inner |
+| 3  | Leaf  |
+| 4  | Leaf  |
+| 5  | Leaf  |
++----+-------+
+<strong>Explanation:</strong> 
+Node 1 is the root node because its parent node is null and it has child nodes 2 and 3.
+Node 2 is an inner node because it has parent node 1 and child node 4 and 5.
+Nodes 3, 4, and 5 are leaf nodes because they have parent nodes and they do not have child nodes.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2021/10/22/tree2.jpg" style="width: 64px; height: 65px;" />
+<pre>
+<strong>Input:</strong> 
+Tree table:
++----+------+
+| id | p_id |
++----+------+
+| 1  | null |
++----+------+
+<strong>Output:</strong> 
++----+-------+
+| id | type  |
++----+-------+
+| 1  | Root  |
++----+-------+
+<strong>Explanation:</strong> If there is only one node on the tree, you only need to output its root attributes.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Note:</strong> This question is the same as <a href="https://leetcode.com/problems/binary-tree-nodes/description/" target="_blank"> 3054: Binary Tree Nodes.</a></p>

Solutions/0608-tree-node/solution.sql

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+SELECT 
+    id, 
+    CASE
+        WHEN p_id IS NULL THEN "Root"
+        WHEN id IN (SELECT p_id FROM Tree) THEN "Inner"
+        ELSE "Leaf"
+    END AS TYPE
+FROM Tree