Leetcode #1369: Get the Second Most Recent Activity
In this guide, we solve Leetcode #1369 Get the Second Most Recent Activity 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: UserActivity +---------------+---------+ | Column Name | Type | +---------------+---------+ | username | varchar | | activity | varchar | | startDate | Date | | endDate | Date | +---------------+---------+ This table may contain duplicates rows. This table contains information about the activity performed by each user in a period of time.
Quick Facts
- Difficulty: Hard
- 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 |
+---------------+---------+
| username | varchar |
| activity | varchar |
| startDate | Date |
| endDate | Date |
+---------------+---------+
This table may contain duplicates rows.
This table contains information about the activity performed by each user in a period of time.
A person with username performed an activity from startDate to endDate.
Python Solution
import duckdb
import pandas as pd
def solution(user_activity: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("UserActivity", user_activity)
return con.execute("""SELECT
username,
activity,
startdate,
enddate
FROM
(
SELECT
*,
RANK() OVER (
PARTITION BY username
ORDER BY startdate DESC
) AS rk,
COUNT(username) OVER (PARTITION BY username) AS cnt
FROM UserActivity
) AS a
WHERE a.rk = 2 OR a.cnt = 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.