100. User Activity for the Past 30 Days I

[문제]

https://leetcode.com/problems/user-activity-for-the-past-30-days-i/description/

 

[풀이]

1. 특정 기간 사이의 행들만 필터링 (between 메소드 사용)

2. 날짜별로 그룹화해서 고유 유저 수를 센다 (nunique 메소드 사용)

3. 컬럼명 변경 (rename 메소드 사용)

 

Pandas

import pandas as pd

def user_activity(activity: pd.DataFrame) -> pd.DataFrame:
    return activity[activity['activity_date'].between('2019-06-28', '2019-07-27')].groupby('activity_date')['user_id'].nunique().reset_index().rename(columns={'activity_date':'day', 'user_id':'active_users'})

 

SQL

SELECT 
    activity_date AS day
    , COUNT(DISTINCT user_id) AS active_users
FROM Activity
WHERE activity_date BETWEEN '2019-06-28' AND '2019-07-27'
GROUP BY activity_date