[HackerRank] Binary Tree Nodes (MySQL)

https://www.hackerrank.com/challenges/binary-search-tree-1/problem?isFullScreen=true&h_r=next-challenge&h_v=zen 

Binary Tree Nodes | HackerRank

 

문제

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:

풀이

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) node
from BST
order by n