leetcode - 608. Tree Node

난이도 : Medium

 

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.

 

 

SELECT id
     , CASE WHEN p_id IS NULL THEN 'Root'
            WHEN id IN (SELECT p_id
                        FROM Tree
                        ) THEN 'Inner'
       ELSE 'Leaf' END type
FROM tree

Accepted (5.01%)