Is Binary Tree Nodes easy or hard?

Binary Tree Nodes is generally considered Medium because it requires recognizing a self join pattern in SQL. Once you understand how to detect child rows with a LEFT JOIN, the classification logic becomes straightforward.

Binary Tree Nodes Python/Java solution

This problem is typically solved using SQL rather than Python or Java because the data already exists in a database table. The core logic relies on a self LEFT JOIN and CASE expression to classify nodes directly within the query.

How to solve Binary Tree Nodes in O(n)?

Use a self LEFT JOIN between the tree table and itself on id = parent_id. This reveals whether a node has child rows. Combine that with a CASE expression: parent_id IS NULL means Root, a matched child row means Inner, otherwise Leaf. The database processes rows in a single join pass, giving about O(n) complexity.

What is the best approach for Binary Tree Nodes?

The best approach uses a SQL self LEFT JOIN. Join the table with itself where a node's id matches another row's parent_id to detect children. Then use a CASE statement to label nodes as Root (no parent), Inner (has children), or Leaf (no children). This runs in roughly O(n) time depending on indexing.

Is Binary Tree Nodes asked at Google/Amazon/Meta?

SQL hierarchy and tree classification problems appear in database-focused interviews at companies like Amazon and Meta. Variations of this problem test understanding of self joins, CASE expressions, and relational modeling of hierarchical data.

What data structure is used in Binary Tree Nodes?

The logical structure is a tree, but it is stored in a relational database table using parent-child references. Each row stores a node id and a parent_id. SQL joins are then used to reconstruct relationships between nodes.

What is the time complexity of Binary Tree Nodes?

The typical SQL solution using a self LEFT JOIN runs in O(n) time for n rows in the tree table. The database scans rows and resolves the join to identify child relationships. Space complexity is O(1) extra since the classification happens within the query.

3054. Binary Tree Nodes - Practice Online

Table: Tree

+-------------+------+ 
| Column Name | Type | 
+-------------+------+ 
| N           | int  | 
| P           | int  |
+-------------+------+
N is the column of unique values for this table.
Each row includes N and P, where N represents the value of a node in Binary Tree, and P is the parent of N.

Write a solution to find the node type of the Binary Tree. Output one of the following for each node:

Root: if the node is the root node.
Leaf: if the node is the leaf node.
Inner: if the node is neither root nor leaf node.

Return the result table ordered by node value in ascending order.

The result format is in the following example.

Example 1:

Input: 
Tree table:
+---+------+
| N | P    | 
+---+------+
| 1 | 2    |
| 3 | 2    | 
| 6 | 8    | 
| 9 | 8    | 
| 2 | 5    | 
| 8 | 5    | 
| 5 | null | 
+---+------+
Output: 
+---+-------+
| N | Type  | 
+---+-------+
| 1 | Leaf  | 
| 2 | Inner |
| 3 | Leaf  |
| 5 | Root  |
| 6 | Leaf  |
| 8 | Inner |
| 9 | Leaf  |    
+---+-------+
Explanation: 
- Node 5 is the root node since it has no parent node.
- Nodes 1, 3, 6, and 9 are leaf nodes because they don't have any child nodes.
- Nodes 2, and 8 are inner nodes as they serve as parents to some of the nodes in the structure.

Note: This question is the same as 608: Tree Node.