Leetcode #1270: All People Report to the Given Manager
In this guide, we solve Leetcode #1270 All People Report to the Given Manager in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
Table: Employees +---------------+---------+ | Column Name | Type | +---------------+---------+ | employee_id | int | | employee_name | varchar | | manager_id | int | +---------------+---------+ employee_id is the column of unique values for this table. Each row of this table indicates that the employee with ID employee_id and name employee_name reports his work to his/her direct manager with manager_id The head of the company is the employee with employee_id = 1.
Quick Facts
- Difficulty: Medium
- Premium: Yes
- Tags: Database
Intuition
The task is relational in nature, which maps cleanly to DataFrame operations in Python.
By treating tables as DataFrames, joins and group-bys become concise and readable.
Approach
Load the inputs as DataFrames and apply the appropriate merge, filter, or group-by.
Select or rename the columns to match the required output.
Steps:
- Load inputs as DataFrames.
- Apply merge/groupby/filter operations.
- Select the output columns.
Example
+---------------+---------+
| Column Name | Type |
+---------------+---------+
| employee_id | int |
| employee_name | varchar |
| manager_id | int |
+---------------+---------+
employee_id is the column of unique values for this table.
Each row of this table indicates that the employee with ID employee_id and name employee_name reports his work to his/her direct manager with manager_id
The head of the company is the employee with employee_id = 1.
Python Solution
import duckdb
import pandas as pd
def solution(employees: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Employees", employees)
return con.execute("""SELECT e1.employee_id
FROM
Employees AS e1
JOIN Employees AS e2 ON e1.manager_id = e2.employee_id
JOIN Employees AS e3 ON e2.manager_id = e3.employee_id
WHERE e1.employee_id != 1 AND e3.manager_id = 1;""").df()
Complexity
The time complexity is O(n log n) (typical). The space complexity is O(n).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.