[MySQL/Hackerrank] Binary Tree Nodes

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

 

Explanation

The Binary Tree below illustrates the sample:

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

11/15일 2차풀이 - 3분