Live-Code Four Cart Features | Dataford Interview Questions

Live-code four features in Instacart's provided Android interview project (Kotlin expected) around the items purchased in a shopping cart.

Asked in the technical phone screen stage. The middle of the post is points-walled, so feature details are not visible. For this algorithmic version, implement the four core behaviors with a pure function: add an item, remove an item, update quantity, and calculate the cart subtotal.

Input and Output

items is a list of dictionaries with id, name, price_cents, and quantity. operations is a list of dictionaries. Return {"items": [...], "total_cents": number} with items sorted by id. An add of an existing item increases its quantity. Removing an unknown item is a no-op. Setting quantity to zero removes the item.

Constraints

0 <= len(items) <= 10^4
0 <= len(operations) <= 10^4
Item IDs are unique within items and operations refer to valid items for update operations
0 <= price_cents <= 10^7
0 <= quantity <= 10^4
All prices and totals are represented in integer cents

Function Signature

def cart_features(items, operations):

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