Find the top 2 highest-paid employees in the `"Engineering"` department.

Problem Statement

<p>Find the top 2 highest-paid <code>employees</code> in the <code>"Engineering"</code> department.</p>

Examples

Input: employees collection: +-----+---------+-------------+--------+ | _id | name | dept | salary | +-----+---------+-------------+--------+ | 1 | Alice | Engineering | 120000 | | 2 | Bob | Marketing | 80000 | | 3 | Charlie | Engineering | 95000 | | 4 | Dana | Engineering | 110000 | +-----+---------+-------------+--------+

Output: +-----+-------+-------------+--------+ | _id | name | dept | salary | +-----+-------+-------------+--------+ | 1 | Alice | Engineering | 120000 | | 4 | Dana | Engineering | 110000 | +-----+-------+-------------+--------+

Explanation: The collection documents are sorted according to the specified field order.

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Use db.<collection>.aggregate([ ... ]) to run a multi-stage data processing pipeline. 💡 Hint 2: Order pipeline stages logically (e.g. $match early to filter documents before processing). 💡 Hint 3: Convert the aggregation cursor using .toArray() at the end of the function.

Editorial & Approach

Problem Overview & Intuition

To solve "Match + Sort + Limit (Top N)", we query the MongoDB document store. The goal is to find the top 2 highest-paid employees in the `"engineering"` department. Using an aggregation pipeline, the database engine filters and structures the BSON documents efficiently.

Step-by-Step Approach

Identify Target Collection: Access the collection through the db instance.
Construct Query / Pipeline: Build the aggregation stages ($match, $group, $sort, etc.).
Resolve Cursor: Invoke .toArray() to transform the query cursor into the required array of documents.

Optimal Implementation (MongoDB)

function solve(db) {
  return db.employees.aggregate([
    { $match: { dept: "Engineering" } },
    { $sort: { salary: -1 } },
    { $limit: 2 }
  ]);
}

Complexity Analysis

Time Complexity O(N) pipeline traversal through aggregation stages.

Space Complexity O(M) intermediate document buffer in aggregation pipeline.

Key Considerations & Edge Cases

Empty Collections: If no documents match, the query cleanly returns an empty array [].
Missing / NULL Fields: Missing fields in documents are handled safely without throwing runtime exceptions.
Type Coercion: BSON types (ObjectId, Numbers, Strings) are compared strictly according to MongoDB specifications.

Match + Sort + Limit (Top N)

Medium

Find the top 2 highest-paid employees in the "Engineering" department.

Example Scenarios

1Example 1

Input:

employees collection

_id	name	dept	salary
1	Alice	Engineering	120000
2	Bob	Marketing	80000
3	Charlie	Engineering	95000
4	Dana	Engineering	110000

Output:

_id	name	dept	salary
1	Alice	Engineering	120000
4	Dana	Engineering	110000

Explanation:

The collection documents are sorted according to the specified field order.

MongoDB Editor

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Query Results (JSON)

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