Incremental Shopping Cart System | Dataford Interview Questions

Build a shopping cart management system, starting simple with requirements added incrementally.

Asked in the live coding stage. Unit tests and TDD expected.

Contract

Implement shopping_cart(operations). Each operation is a dictionary with action add, set_quantity, remove, or total. add increases an item's quantity and replaces its unit price with the supplied price. set_quantity replaces the quantity, removing the item when the quantity is zero. Mutations append None; total appends the sum of price multiplied by quantity for all items. Return the results list.

Constraints

0 <= operations.length <= 10^4
Each operation has a valid action
item_id is a non-empty string
price and quantity are non-negative integers
An item exists before set_quantity is used
Each total fits in a Python integer

Function Signature

def shopping_cart(operations):

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Problem