Most Connected User by Accepted Requests

Medium

You are given accepted friendship request logs in table RequestAccepted. Each row represents one accepted connection between two different users: requester_id: user who sent the request accepter_id: user who accepted the request accept_date: date of acceptance Interpret each row as an undirected friendship edge. That means both requester_id and accepter_id gain one friend from that row. Task: Return the user with the highest total number of friends. Return exactly these columns: id: user id num: friend count The test data guarantees exactly one user has the highest friend count. Supported submission environments: SQL (SQLite 3.27.2) Pandas (Python)

Example 1

Input

RequestAccepted:
| requester_id | accepter_id | accept_date |
|--------------|-------------|-------------|
| 1            | 2           | 2016-06-03  |
| 1            | 3           | 2016-06-08  |
| 2            | 3           | 2016-06-08  |
| 3            | 4           | 2016-06-09  |

Output

[{"id":3,"num":3}]

Explanation

User 3 is connected to users 1, 2, and 4, so their friend count is 3, which is the highest.

Example 2

Input

RequestAccepted:
| requester_id | accepter_id | accept_date |
|--------------|-------------|-------------|
| 10           | 20          | 2020-01-01  |
| 30           | 20          | 2020-01-02  |
| 40           | 20          | 2020-01-03  |
| 30           | 40          | 2020-01-04  |

Output

[{"id":20,"num":3}]

Explanation

User 20 appears in three accepted relationships, while other users appear fewer times.

Example 3

Input

RequestAccepted:
| requester_id | accepter_id | accept_date |
|--------------|-------------|-------------|
| 100          | 101         | 2021-04-01  |
| 102          | 101         | 2021-04-02  |
| 103          | 101         | 2021-04-03  |
| 104          | 103         | 2021-04-04  |
| 105          | 106         | 2021-04-05  |

Output

[{"id":101,"num":3}]

Explanation

User 101 appears in three accepted pairs, while every other user appears at most twice, so user 101 is the unique leader.

Constraints

2 <= number of rows in RequestAccepted <= 200000
1 <= requester_id, accepter_id <= 1000000000
requester_id != accepter_id
(requester_id, accepter_id) pairs are unique
At most one accepted row exists for any unordered user pair
accept_date is a valid date string
Exactly one user has the strictly highest friend count
Use SQLite 3.27.2 semantics for SQL submissions
For Pandas submissions, return a DataFrame with columns id and num

RequestAccepted: | requester_id | accepter_id | accept_date | |--------------|-------------|-------------| | 1 | 2 | 2016-06-03 | | 1 | 3 | 2016-06-08 | | 2 | 3 | 2016-06-08 | | 3 | 4 | 2016-06-09 |

RequestAccepted: | requester_id | accepter_id | accept_date | |--------------|-------------|-------------| | 10 | 20 | 2020-01-01 | | 30 | 20 | 2020-01-02 | | 40 | 20 | 2020-01-03 | | 30 | 40 | 2020-01-04 |

RequestAccepted: | requester_id | accepter_id | accept_date | |--------------|-------------|-------------| | 100 | 101 | 2021-04-01 | | 102 | 101 | 2021-04-02 | | 103 | 101 | 2021-04-03 | | 104 | 103 | 2021-04-04 | | 105 | 106 | 2021-04-05 |