question 342 Algorithms & Complexity · easy

Fix the unknown-SKU report

Before an import, a script lists the SKUs in incoming orders that aren't in the product catalogue (a dictionary from SKU to product name). It reports every SKU as unknown, even ones the catalogue clearly has, and it is slow on a big catalogue. Find the bug and fix it without changing what the report should contain.

Functionunknown_skus(order_skus, catalogue)

cataloguea dictionary: SKU → product name (a name may be an empty string while it is being written)

Returnseach SKU from order_skus that is not a key of the catalogue, once, in the order first seen

Examples

callunknown_skus(['HOM-22847', 'GRO-10442', 'SPO-11681', 'GRO-10442'], {'SPO-11681': 'Ultra Bike Light', 'HOM-22847': 'Deluxe Vase', 'ELE-24781': 'Organic Speaker'})returns['GRO-10442']

callunknown_skus(['BOO-58412', 'HOM-52782'], {'SPO-11681': 'Ultra Bike Light', 'HOM-22847': 'Deluxe Vase', 'ELE-24781': 'Organic Speaker'})returns['BOO-58412', 'HOM-52782']

callunknown_skus(['ELE-24781'], {'SPO-11681': 'Ultra Bike Light', 'HOM-22847': 'Deluxe Vase', 'ELE-24781': 'Organic Speaker'})returns[]