HackerRank SQL

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

Solution(MySQL)

select N,
       if(P is null, 'Root', if((select count(*) from BST where P = B.N)> 0, 'Inner', 'Leaf')) 
from BST as B 
order by N;

Solution(SQL Server):

select N,
       case when P is null then 'Root'
            when (select count(*) from BST where P = B.N) > 0 then  
            'Inner'
            else 'Leaf'
       end
from BST as B 
order by N
;

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