Impact Interview Exercise
Implement the code for a checkout system that handles pricing schemes such as “apples cost 50p each or three apples cost 130p”.
Implement the code for a supermarket checkout that calculates the total price of a number of items. In a normal supermarket, things are identified using Stock Keeping Units (or SKUs).
In our store, we’ll use individual letters of the alphabet (A, B, C and so on..). Our goods are priced individually.
In addition, some items are multi-priced: buy N of them, and they’ll cost you Y pence.
For example, item ‘A’ might cost 50p individually, but this week we have a special offer: buy three A’s and they’ll cost you 130p. The prices are:
| SKU | Unit Price | Special Price |
|---|---|---|
| A | 50 | 3 for 130 |
| B | 30 | 2 for 45 |
| C | 20 | |
| D | 15 |
The checkout should accept the items in any order, so that if we scan a B, an A and another B, it’ll recognize the two B’s and price them at 45p (for a total price of 95p).
The pricing rules change frequently, bear this in mind with your implementation.
The interface to the checkout should be:
interface CheckoutInterface
{
/**
* Adds an item to the checkout
*
* @param $sku string
*/
public function scan(string $sku);
/**
* Calculates the total price of all items in this checkout
*
* @return int
*/
public function total(): int;
}