[HackerRank] Binary Tree Nodes

 

 

[문제]

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[MySQL]

SELECT DISTINCT b1.N
     , CASE WHEN b1.P IS NULL THEN 'Root'
            WHEN b2.P IS NULL THEN 'Leaf'
            ELSE 'Inner'
        END AS type
FROM BST AS b1
    LEFT JOIN BST AS b2 ON b1.N = b2.P
ORDER BY b1.N ASC