[MySQL/HackerRank] Binary Tree Nodes

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.

Sample Input

Sample Output

1 Leaf
2 Inner
3 Leaf
5 Root
6 Leaf
8 Inner
9 Leaf

The Binary Tree below illustrates the sample:

SELECT
    N,
    CASE
        WHEN P IS NULL THEN 'Root'
        WHEN N NOT IN (SELECT P FROM BST WHERE P IS NOT NULL) THEN 'Leaf'
        ELSE 'Inner'
    END AS NodeType
FROM BST
ORDER BY N;

 

 

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