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Java-based LeetCode algorithm problem solutions, regularly updated

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608\. Tree Node

Medium

SQL Schema

Table: `Tree`

    +-------------+------+
    | Column Name | Type |
    +-------------+------+
    | id          | int  |
    | p_id        | int  |
    +-------------+------+
    id is the primary key column 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. 

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 an SQL query to report the type of each node in the tree.

Return the result table **ordered** by `id` **in ascending order**.

The query result format is in the following example.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/10/22/tree1.jpg)

**Input:**

    Tree table:
    +----+------+
    | id | p_id |
    +----+------+
    | 1  | null |
    | 2  | 1    |
    | 3  | 1    |
    | 4  | 2    |
    | 5  | 2    |
    +----+------+

**Output:**

    +----+-------+
    | id | type  |
    +----+-------+
    | 1 | Root   |
    | 2 | Inner  |
    | 3 | Leaf   |
    | 4 | Leaf   |
    | 5 | Leaf   |
    +----+-------+

**Explanation:**

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. 

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/10/22/tree2.jpg)

**Input:**

    Tree table:
    +----+------+
    | id | p_id |
    +----+------+
    | 1  | null |
    +----+------+

**Output:**

    +----+-------+
    | id | type  |
    +----+-------+
    | 1  | Root  |
    +----+-------+

**Explanation:** If there is only one node on the tree, you only need to output its root attributes.