Leetcode #1709: Biggest Window Between Visits
In this guide, we solve Leetcode #1709 Biggest Window Between Visits 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: UserVisits +-------------+------+ | Column Name | Type | +-------------+------+ | user_id | int | | visit_date | date | +-------------+------+ This table does not have a primary key, it might contain duplicate rows. This table contains logs of the dates that users visited a certain retailer.
Quick Facts
- Difficulty: Medium
- Premium: Yes
- 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 |
| visit_date | date |
+-------------+------+
This table does not have a primary key, it might contain duplicate rows.
This table contains logs of the dates that users visited a certain retailer.
Python Solution
import duckdb
import pandas as pd
def solution(user_visits: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("UserVisits", user_visits)
return con.execute("""WITH
T AS (
SELECT
user_id,
DATEDIFF(
LEAD(visit_date, 1, '2021-1-1') OVER (
PARTITION BY user_id
ORDER BY visit_date
),
visit_date
) AS diff
FROM UserVisits
)
SELECT user_id, MAX(diff) AS biggest_window
FROM T
GROUP BY 1
ORDER BY 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.