리트코드 : 1211. Queries Quality and Percentage

리트코드 : 1211. Queries Quality and Percentage

• https://leetcode.com/problems/queries-quality-and-percentage/description/
  

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문제

Table: Queries

+-------------+---------+
| Column Name | Type    |
+-------------+---------+
| query_name  | varchar |
| result      | varchar |
| position    | int     |
| rating      | int     |
+-------------+---------+
This table may have duplicate rows.
This table contains information collected from some queries on a database.
The position column has a value from 1 to 500.
The rating column has a value from 1 to 5. Query with rating less than 3 is a poor query.


We define query as:quality

The average of the ratio between query rating and its position.

We also define as:poor query percentage

The percentage of all queries with rating less than 3.

Write a solution to find each , the and .query_namequalitypoor_query_percentage

Both and should be rounded to 2 decimal places.qualitypoor_query_percentage

Return the result table in any order.

The result format is in the following example.



Example 1:

Input: 
Queries table:
+------------+-------------------+----------+--------+
| query_name | result            | position | rating |
+------------+-------------------+----------+--------+
| Dog        | Golden Retriever  | 1        | 5      |
| Dog        | German Shepherd   | 2        | 5      |
| Dog        | Mule              | 200      | 1      |
| Cat        | Shirazi           | 5        | 2      |
| Cat        | Siamese           | 3        | 3      |
| Cat        | Sphynx            | 7        | 4      |
+------------+-------------------+----------+--------+
Output: 
+------------+---------+-----------------------+
| query_name | quality | poor_query_percentage |
+------------+---------+-----------------------+
| Dog        | 2.50    | 33.33                 |
| Cat        | 0.66    | 33.33                 |
+------------+---------+-----------------------+
Explanation: 
Dog queries quality is ((5 / 1) + (5 / 2) + (1 / 200)) / 3 = 2.50
Dog queries poor_ query_percentage is (1 / 3) * 100 = 33.33

Cat queries quality equals ((2 / 5) + (3 / 3) + (4 / 7)) / 3 = 0.66
Cat queries poor_ query_percentage is (1 / 3) * 100 = 33.33

문제 풀이

MySQL

select query_name,
       round(avg(rating/position),2) as quality,
       round(100*sum(rating<3)/COUNT(*),2) AS poor_query_percentage
from queries
where query_name is not null
group by query_name

• case whem 대신 그냥 조건식을 쓰면 불리언으로 반환돼서 깔끔하게 쓸 수 있다.
• 문제에선 query name이 null인 경우는 원하지 않는다. (테케 12? 13?)
  • is not null로 제거해주기

Pandas

import pandas as pd

def queries_stats(queries: pd.DataFrame) -> pd.DataFrame:
    queries['r/q'] = queries['rating'] / queries['position'] + 1e-10
    queries['poor'] = queries['rating'] < 3
    answer = queries.groupby('query_name').agg(
        quality = ('r/q', lambda x: round(x.mean(),2)),
        poor_query_percentage = ('poor', lambda x: round(100*x.mean(),2))
    ).reset_index()

    return answer

• 비슷한 방식으로 풀이.
• agg 내에서 지정되지 않은 함수를 사용할 때 lambda로 접근
• lambda 내에서도 너무 복잡하게 나오지 않도록 미리 r/q, poor을 구했다.
• round에서 오차가 발생하네용 -> 1e-10 추가

코멘트

• 조건식에 case when 안넣고 그냥 하니까 더 깔끔하고 좋은듯.
• 다중 조건으로 많이 적는 경우에는 case when이 낫겠지만, T/F식으로 나뉘는 경우는 이렇게 푸는게 좋은 듯