Leetcode #1158: Market Analysis I
In this guide, we solve Leetcode #1158 Market Analysis I 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: Users +----------------+---------+ | Column Name | Type | +----------------+---------+ | user_id | int | | join_date | date | | favorite_brand | varchar | +----------------+---------+ user_id is the primary key (column with unique values) of this table. This table has the info of the users of an online shopping website where users can sell and buy items.
Quick Facts
- Difficulty: Medium
- 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 |
+----------------+---------+
| user_id | int |
| join_date | date |
| favorite_brand | varchar |
+----------------+---------+
user_id is the primary key (column with unique values) of this table.
This table has the info of the users of an online shopping website where users can sell and buy items.
Python Solution
import duckdb
import pandas as pd
def solution(users: pd.DataFrame, orders: pd.DataFrame, items: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Users", users)
con.register("Orders", orders)
con.register("Items", items)
return con.execute("""SELECT
u.user_id AS buyer_id,
u.join_date,
COUNT(order_id) AS orders_in_2019
FROM
Users AS u
LEFT JOIN Orders AS o ON u.user_id = o.buyer_id AND YEAR(order_date) = 2019
GROUP BY user_id;""").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.