Find all products that are either in `"Electronics"` category with price over `500`, OR in `"Books"` category.

Problem Statement

<p>Find all <code>products</code> that are either in <code>"Electronics"</code> <code>category</code> with <code>price</code> over <code>500</code>, OR in <code>"<code>Books</code>"</code> <code>category</code>.</p>

Examples

Input: products collection: +-----+--------+-------------+-------+ | _id | name | category | price | +-----+--------+-------------+-------+ | 1 | Laptop | Electronics | 999 | | 2 | Mouse | Electronics | 25 | | 3 | Novel | Books | 15 | | 4 | Tablet | Electronics | 499 | +-----+--------+-------------+-------+

Output: +-----+--------+-------------+-------+ | _id | name | category | price | +-----+--------+-------------+-------+ | 1 | Laptop | Electronics | 999 | | 3 | Novel | Books | 15 | +-----+--------+-------------+-------+

Explanation: The query retrieves all documents from the collection that satisfy the specified filter criteria.

Complexity

Time Complexity: -

Space Complexity: -

Hints

💡 Hint 1: Use comparison operators ($gt, $gte, $lt, $lte) to filter documents based on numeric or date ranges. 💡 Hint 2: Construct the filter condition: { fieldName: { $gt: value } } inside db.<collection>.find(...). 💡 Hint 3: Chain projection or sorting if requested, and invoke .toArray() to produce the result array.

Editorial & Approach

Problem Overview & Intuition

To solve "Complex OR with Nested Conditions", we query the MongoDB document store. The goal is to find all products that are either in `"electronics"` category with price over `500`, or in `"books"` category. Using a targeted find query, 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 query filter with appropriate comparison operators.
Resolve Cursor: Invoke .toArray() to transform the query cursor into the required array of documents.

Optimal Implementation (MongoDB)

function solve(db) {
  return db.products.find({ $or: [{ category: "Electronics", price: { $gt: 500 } }, { category: "Books" }] }).toArray();
}

Complexity Analysis

Time Complexity O(N) collection scan (O(log N) if index is present on filtered fields).

Space Complexity O(K) where K is the number of returned documents in memory.

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.

Complex OR with Nested Conditions

Medium

Find all products that are either in "Electronics" category with price over 500, OR in "Books" category.

Example Scenarios

1Example 1

Input:

products collection

_id	name	category	price
1	Laptop	Electronics	999
2	Mouse	Electronics	25
3	Novel	Books	15
4	Tablet	Electronics	499

Output:

_id	name	category	price
1	Laptop	Electronics	999
3	Novel	Books	15

Explanation:

The query retrieves all documents from the collection that satisfy the specified filter criteria.

MongoDB Editor

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Query Results (JSON)

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