Get all distinct `city` values from orders where `amount` is greater than `100`.

Problem Statement

<p>Get all distinct <code>city</code> values from <code>orders</code> where <code>amount</code> is greater than <code>100</code>.</p>

Examples

Input: orders collection: +-----+---------+--------+ | _id | city | amount | +-----+---------+--------+ | 1 | NYC | 150 | | 2 | LA | 50 | | 3 | NYC | 200 | | 4 | Chicago | 300 | | 5 | LA | 120 | +-----+---------+--------+

Output: +---------+ | result | +---------+ | NYC | | Chicago | | LA | +---------+

Explanation: The target document is modified according to the update operators and the updated document is returned.

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 "Distinct with Filter", we query the MongoDB document store. The goal is to get all distinct `city` values from orders where `amount` is greater than `100`. 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.orders.distinct("city", { amount: { $gt: 100 } });
}

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.

Distinct with Filter

Medium

Get all distinct city values from orders where amount is greater than 100.

Example Scenarios

1Example 1

Input:

orders collection

_id	city	amount
1	NYC	150
2	LA	50
3	NYC	200
4	Chicago	300
5	LA	120

Output:

result
NYC
Chicago
LA

Explanation:

The target document is modified according to the update operators and the updated document is returned.

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Query Results (JSON)

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