This Leetcode problem Tree Node LeetCode Solution is done in SQL.

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Tree Node LeetCode Solution

Problem Statement

Column Name	Type
id	int
p_id	int

id is the column with unique values for this table. Each row of this table contains information about the id of a node and the id of its parent node in a tree. The given structure is always a valid tree.

Each node in the tree can be one of three types:

• “Leaf”: if the node is a leaf node.
• “Root”: if the node is the root of the tree.
• “Inner”: If the node is neither a leaf node nor a root node.

Write a solution to report the type of each node in the tree.

Return the result table in any order.

The result format is in the following example.

Example 1:

Input:

id	p_id
1	null
2	1
3	1
4	2
5	2

Output:

id	type
1	Root
2	Inner
3	Leaf
4	Leaf
5	Leaf

Explanation:
Node 1 is the root node because its parent node is null and it has child nodes 2 and 3.
Node 2 is an inner node because it has parent node 1 and child node 4 and 5.
Nodes 3, 4, and 5 are leaf nodes because they have parent nodes and they do not have child nodes.

Example 2:

Input:

id	p_id
1	null

Output:

id	type
1	Root

Explanation: If there is only one node on the tree, you only need to output its root attributes.

Tree Node LeetCode Solution MySQL

select 
  id, 
  case when p_id is null then 'Root' when p_id is not null 
  and id in (
    select 
      distinct p_id 
    from 
      tree
  ) then 'Inner' else 'Leaf' end as Type 
from 
  tree;Code language: SQL (Structured Query Language) (sql)