How do you solve Managers with at Least 5 Direct Reports on LeetCode?

Managers with at Least 5 Direct Reports (LeetCode #570) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Using aggregation functions can greatly simplify counting tasks.

What is the time complexity of Managers with at Least 5 Direct Reports?

The optimal solution for Managers with at Least 5 Direct Reports runs in O(n) time and uses O(n) space. This complexity is linear because we are only scanning through the Employee table a couple of times, once for counting and once for joining.

What is the brute force solution for Managers with at Least 5 Direct Reports?

The brute force approach for Managers with at Least 5 Direct Reports is Brute Force, with O(n²) time complexity and O(1) space complexity. In this approach, we will check each employee to see how many direct reports they have by counting how many employees list them as their manager. It's straightforward but inefficient. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Managers with at Least 5 Direct Reports?

Managers with at Least 5 Direct Reports uses the following concepts: Database. The recommended patterns to study are: Hash Map, Aggregation, Join.

What are the interview tips for Managers with at Least 5 Direct Reports?

Always think about how to reduce nested queries for efficiency. Practice writing SQL queries with GROUP BY and JOIN to become comfortable with them. Explain your thought process clearly when writing queries.

What are common mistakes when solving Managers with at Least 5 Direct Reports?

Not using GROUP BY correctly, leading to incorrect counts. Overlooking NULL values in managerId when counting.

#570

Managers with at Least 5 Direct Reports

Medium

DatabaseHash MapAggregationJoin

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

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Intuition

Time O(n)Space O(n)

We can leverage SQL's aggregation functions to efficiently count the number of direct reports for each manager in one go, reducing the need for nested queries.

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Algorithm

3 steps

1Step 1: Use GROUP BY on managerId to count the number of employees reporting to each manager.
2Step 2: Filter the results to only include managers with a count of 5 or more.
3Step 3: Join this result with the Employee table to get the names of those managers.

solution.py2 lines

1# Full working Python code
2SELECT e.name FROM Employee e JOIN (SELECT managerId FROM Employee GROUP BY managerId HAVING COUNT(*) >= 5) m ON e.id = m.managerId;

ℹ

Complexity note: This complexity is linear because we are only scanning through the Employee table a couple of times, once for counting and once for joining.

1Using aggregation functions can greatly simplify counting tasks.
2Joining tables can help retrieve related information efficiently.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.