Leetcode #1341: Movie Rating
In this guide, we solve Leetcode #1341 Movie Rating 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: Movies +---------------+---------+ | Column Name | Type | +---------------+---------+ | movie_id | int | | title | varchar | +---------------+---------+ movie_id is the primary key (column with unique values) for this table. title is the name of the movie.
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 |
+---------------+---------+
| movie_id | int |
| title | varchar |
+---------------+---------+
movie_id is the primary key (column with unique values) for this table.
title is the name of the movie.
Each movie has a unique title.
Python Solution
import duckdb
import pandas as pd
def solution(movies: pd.DataFrame, users: pd.DataFrame, movie_rating: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Movies", movies)
con.register("Users", users)
con.register("MovieRating", movie_rating)
return con.execute("""(
SELECT name AS results
FROM
Users
JOIN MovieRating USING (user_id)
GROUP BY user_id
ORDER BY COUNT(1) DESC, name
LIMIT 1
)
UNION ALL
(
SELECT title
FROM
MovieRating
JOIN Movies USING (movie_id)
WHERE DATE_FORMAT(created_at, '%Y-%m') = '2020-02'
GROUP BY movie_id
ORDER BY AVG(rating) DESC, title
LIMIT 1
);""").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.