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

 

 

 

 

 

 

 

 

# 나의 해답

 

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