584. Find Customer Referee

EasyLeetCode

Column Name	Type
id	int
name	varchar
referee_id	int

In SQL, id is the primary key column for this table.

Each row of this table indicates the id of a customer, their name, and the id of the customer who referred them.

Find the names of the customer that are not referred by the customer with id = 2.

Return the result table in any order.

The result format is in the following example.

Example 1:

Input: Customer table:

id	name	referee_id
1	Will	null
2	Jane	null
3	Alex	2
4	Bill	null
5	Zack	1
6	Mark	2

Output:

name
Will
Jane
Bill
Zack

How to solve the problem

SQL or Pandas

Code

import pandas as pd

def find_customer_referee(customer: pd.DataFrame) -> pd.DataFrame:
    result = customer[(customer['referee_id'] != 2) | (customer['referee_id'].isnull())][['name']]
    return result

SELECT name FROM Customer WHERE referee_id IS NULL OR referee_id != 2;

Complexity

Time complexity: O(1)

Space complexity: O(1)