Classes With at Least 5 Students — LeetCode 596 Python Solution

The problem

Report every class that has five or more students enrolled, in any order. The Courses table has one row per enrolment: student (varchar) and class (varchar), with the pair (student, class) as the primary key.

Example

Courses table:

| student | class   |
| ------- | ------- |
| Ada     | Math    |
| Bob     | Math    |
| Cara    | Math    |
| Dan     | Math    |
| Eve     | Math    |
| Ada     | Biology |
| Bob     | Biology |

Result:

| class |
| ----- |
| Math  |

Math has five enrolments and clears the bar; Biology has two and does not.

Python solution

import pandas as pd

def classes_with_5_students(courses: pd.DataFrame) -> pd.DataFrame:
    counts = courses.groupby('class')['student'].nunique()
    res = counts[counts >= 5].reset_index()[['class']]
    return res

Complexity

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