Added Tree node

Author: thecoddiwompler

Tree Node/READme.md

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+# [Tree Node](https://leetcode.com/problems/tree-node/)
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+
+---
+
+## 🛠️ Problem Statement
+
+  <b>Table Name : Queue</b>
+
+|  Column Name  |Type |
+| ------------- | ------------- |
+| id   | int     |
+| p_id | varchar |
+
+* <b>id is the column with unique values for this table. </b>
+* Each row of this table contains information about the id of a node and the id of its parent node in a tree (represented by p_id).
+* The given structure is always a valid tree.
+<br/>
+
+Each node in the tree can be one of three types:
+
+* "Leaf": if the node is a leaf node.
+* "Root": if the node is the root of the tree.
+* "Inner": If the node is neither a leaf node nor a root node.
+
+Write a solution to report the type of each node in the tree.
+
+Return the result table in any order.
+
+The result format is in the following example.
+
+![Sample Example](./img/tree1.jpg)
+
+</br>
+
+ <details>
+<summary>
+Input
+</summary>
+<br>
+  
+  <b>Table Name: Queue</b>
+
+| id | p_id | 
+| --- |------ | 
+| 1  | null |
+| 2  | 1    |
+| 3  | 1    |
+| 4  | 2    |
+| 5  | 2    |
+
+</details>
+
+<details>
+<summary>
+Output
+</summary>
+<br>
+
+| id |  type |
+| ---- |  ----|
+| 1  | Root  |
+| 2  | Inner |
+| 3  | Leaf  |
+| 4  | Leaf  |
+| 5  | Leaf  |
+
+</details>
+
+---

Tree Node/img/tree1.jpg

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+CREATE TABLE IF NOT EXISTS Tree (id int, p_id int);
+
+TRUNCATE TABLE Tree;
+
+INSERT INTO
+    Tree (id, p_id)
+VALUES
+    ('1', NULL);
+
+INSERT INTO
+    Tree (id, p_id)
+VALUES
+    ('2', '1');
+
+INSERT INTO
+    Tree (id, p_id)
+VALUES
+    ('3', '1');
+
+INSERT INTO
+    Tree (id, p_id)
+VALUES
+    ('4', '2');
+
+INSERT INTO
+    Tree (id, p_id)
+VALUES
+    ('5', '2');
+
+COMMIT;

Tree Node/schema.sql

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+WITH cte AS (
+    SELECT
+        a.id,
+        a.p_id,
+        b.id c_id
+    FROM
+        tree a
+        LEFT JOIN tree b ON a.id = b.p_id
+)
+SELECT
+    id,
+    CASE
+        WHEN p_id IS NULL THEN 'Root'
+        WHEN c_id IS NULL THEN 'Leaf'
+        ELSE 'Inner'
+    END AS TYPE
+FROM
+    cte
+GROUP BY
+    id,
+    CASE
+        WHEN p_id IS NULL THEN 'Root'
+        WHEN c_id IS NULL THEN 'Leaf'
+        ELSE 'Inner'
+    END