How do you solve Project Employees I on LeetCode?

Project Employees I (LeetCode #1075) 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 JOINs effectively can reduce the need for nested loops.

What is the time complexity of Project Employees I?

The optimal solution for Project Employees I runs in O(n) time and uses O(n) space. This complexity is linear because we are effectively scanning through the joined dataset once to compute the averages.

What is the brute force solution for Project Employees I?

The brute force approach for Project Employees I is Brute Force, with O(n²) time complexity and O(1) space complexity. In the brute force approach, we will calculate the average experience for each project by iterating through all employees for each project. This is straightforward but inefficient, especially with larger datasets. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Project Employees I?

Project Employees I uses the following concepts: Database. The recommended patterns to study are: Hash Map, Aggregation.

What are the interview tips for Project Employees I?

Always clarify the requirements before jumping into the solution. Think about edge cases, such as projects with no employees. Practice writing SQL queries to become familiar with JOINs and aggregation.

What are common mistakes when solving Project Employees I?

Not using GROUP BY correctly, leading to incorrect averages. Forgetting to round the average to 2 decimal places.

#1075

Project Employees I

Easy

DatabaseHash MapAggregation

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)

The optimal approach uses SQL's aggregation functions to compute averages directly, leveraging joins and grouping to minimize the number of operations needed.

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Algorithm

5 steps

1Step 1: Join the Project and Employee tables on employee_id.
2Step 2: Use GROUP BY to group results by project_id.
3Step 3: Calculate the average experience_years for each project using AVG() function.
4Step 4: Round the average to 2 decimal places.
5Step 5: Select project_id and the rounded average as output.

solution.py4 lines

1SELECT p.project_id, ROUND(AVG(e.experience_years), 2) AS average
2FROM Project p
3JOIN Employee e ON p.employee_id = e.employee_id
4GROUP BY p.project_id;

ℹ

Complexity note: This complexity is linear because we are effectively scanning through the joined dataset once to compute the averages.

1Using JOINs effectively can reduce the need for nested loops.
2Aggregation functions like AVG() simplify calculations.

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