[HackerRank] Advanced Select > 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:

 

[MySQL Solution]

select N,
    case
        when P is null then 'Root'
        when N in (select P from BST) then 'Inner'
        else 'Leaf'
    end as type
from BST
order by N;

 

 

문제 링크:

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