Problem statement

In a busy retail environment, cashiers scan barcodes rapidly. The checkout system must instantly look up the price associated with each scanned SKU (Stock Keeping Unit). Occasionally, a barcode might be damaged or missing from the database, so the system must handle unrecognized scans gracefully without crashing the register.

Task requirements

• Create a CheckoutSystem class within a defined namespace.

• Maintain a running total of the transaction within the class.

• Implement a ScanItem(string sku) method that attempts to find the price of the scanned barcode.

• If the item exists, add its price to the running total and print the scanned item's price to the console.

• If the item does not exist, print an “Unknown barcode” warning without altering the total.

Constraints

• You must use a Dictionary<string, decimal> to store the product catalog.

• Initialize the dictionary with at least three products using target-typed new() and a collection initializer block { }.

• You must strictly avoid using the bracket indexer [] to look up prices dynamically, as this will throw a KeyNotFoundException for missing items.

• You must use the TryGetValue() method to safely check for the SKU and retrieve the price in a single $O(1)$ operation.

Good luck trying the exercise! If you’re unsure how to proceed, check the “Solution” tab above.

Get hints

• Use the target-typed syntax new() followed by an initializer block { ["Key"] = Value, } to define your catalog dictionary at the class level.

• The TryGetValue method requires an out parameter to hold the result if the key is found. You can declare this variable inline, like out decimal price.

• TryGetValue returns a boolean. Use it inside an if statement to control the flow between a successful scan and an unknown barcode.