Leetcode #1795: Rearrange Products Table
In this guide, we solve Leetcode #1795 Rearrange Products Table in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
Table: Products +-------------+---------+ | Column Name | Type | +-------------+---------+ | product_id | int | | store1 | int | | store2 | int | | store3 | int | +-------------+---------+ product_id is the primary key (column with unique values) for this table. Each row in this table indicates the product's price in 3 different stores: store1, store2, and store3.
Quick Facts
- Difficulty: Easy
- Premium: No
- Tags: Database
Intuition
The task is relational in nature, which maps cleanly to DataFrame operations in Python.
By treating tables as DataFrames, joins and group-bys become concise and readable.
Approach
Load the inputs as DataFrames and apply the appropriate merge, filter, or group-by.
Select or rename the columns to match the required output.
Steps:
- Load inputs as DataFrames.
- Apply merge/groupby/filter operations.
- Select the output columns.
Example
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| product_id | int |
| store1 | int |
| store2 | int |
| store3 | int |
+-------------+---------+
product_id is the primary key (column with unique values) for this table.
Each row in this table indicates the product's price in 3 different stores: store1, store2, and store3.
If the product is not available in a store, the price will be null in that store's column.
Python Solution
import duckdb
import pandas as pd
def solution(products: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Products", products)
return con.execute("""SELECT product_id, 'store1' AS store, store1 AS price FROM Products WHERE store1 IS NOT NULL
UNION
SELECT product_id, 'store2' AS store, store2 AS price FROM Products WHERE store2 IS NOT NULL
UNION
SELECT product_id, 'store3' AS store, store3 AS price FROM Products WHERE store3 IS NOT NULL;""").df()
Complexity
The time complexity is O(n log n) (typical). The space complexity is O(n).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.