[HackerRank/SQL] Advanced Select - Binary Tree Nodes

Problem. Advanced Select - Binary Tree Nodes

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Link.

https://www.hackerrank.com/challenges/binary-search-tree-1/problem?isFullScreen=true 

Binary Tree Nodes | HackerRank

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Description.

You are given a table, BST, containing two columns: N and P, where N represents the value of a node in Binary Tree, and P is the parent of N.

 

Write a query to find the node type of Binary Tree ordered by the value of the node.

Output one of the following for each node:

• Root: If node is root node
• Leaf: If node is leaf node
• Inner: If node is neither root nor leaf node

입력 예시

출력 예시

BST 예시

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Key Point. 

CASE WHEN,

 

IS,

 

IN,

 

CONCAT,

 

ORDER BY,

 

DISTINCT,

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My Answer. 

SELECT
    CASE 
        WHEN P IS NULL THEN CONCAT(N, ' Root')
        WHEN N IN (SELECT DISTINCT SB.P FROM BST SB) THEN CONCAT(N, ' Inner')
        ELSE CONCAT(N, ' Leaf')
    END
FROM BST
ORDER BY N ASC;

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References.