LeetCode - 608. Tree Node (MySQL)

Medium, SQL - CASE

문제

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.

풀이

• 트리 구조의 데이터를 확인하는 문제
• 그렇게 어렵진 않았다.

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