Friend Requests II: Who Has the Most Friends — LeetCode 602 Python Solution

The problem

Every accepted request makes both people friends. Report the id of the person with the most friends together with that number; the test data guarantees only one person holds the record. The RequestAccepted table has one row per accepted request: requester_id (int), accepter_id (int) and accept_date (date), with the pair (requester_id, accepter_id) as the primary key.

Example

RequestAccepted table:

| requester_id | accepter_id | accept_date |
| ------------ | ----------- | ----------- |
| 11           | 21          | 2024-01-04  |
| 11           | 31          | 2024-01-06  |
| 21           | 31          | 2024-01-09  |
| 31           | 41          | 2024-01-11  |

Result:

| id | num |
| -- | --- |
| 31 | 3   |

User 31 appears in three accepted requests and so has three friends, ahead of 11 and 21 with two each and 41 with one.

Python solution

import pandas as pd

def most_friends(request_accepted: pd.DataFrame) -> pd.DataFrame:
    ids = pd.concat([request_accepted['requester_id'], request_accepted['accepter_id']], ignore_index=True)
    counts = ids.value_counts()
    max_cnt = counts.max()
    person = counts[counts == max_cnt].index.min()
    return pd.DataFrame({'id': [int(person)], 'num': [int(max_cnt)]})

Complexity

Related problems