leetcode_gym/_problems/sql_binary_tree_nodes.md

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layout	title	last_solved	category	leetcode_url	status
page	SQL Binary Tree Nodes		sql	https://www.hackerrank.com/challenges/binary-search-tree-1	Attempted

Problem

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:

Solution

{% highlight sql %}

select n, case when p is null then 'Root' -- case when n not in (2,6,4,15,9,13,11) then 'Leaf' else 'Inner' when n in (select distinct p from bst) then 'Inner' else 'Leaf' end

end from bst order by n;

{% endhighlight %}