Problem Description

Implement a simple food-ordering workflow that processes user selections, updates a shopping cart, applies discounts, and generates a receipt.

You are provided with the following classes:

• Item: Represents a menu item.
• Menu: Manages available Items.
• Display: Handles printing the receipt.

And a function:

• onUserUpdateSelected(itemId): This function is called each time a user adds an item to their cart.

Part 1: Basic Cart and Receipt

Each time onUserUpdateSelected(itemId) is called:

1. Update the user's shopping cart with the newly selected item.
2. Generate and print a receipt via the Display class.
3. The receipt must list all items in the cart, the subtotal, any applied discounts, and the final total.
4. Implement appropriate toString() methods for relevant classes to support receipt printing.

Part 2: Combo Discounts

Introduce a Combo class. Each combo is defined by a set of k specific items that, when present in the cart, yield a discountAmount.

After each item addition (i.e., within onUserUpdateSelected):

1. Identify any valid set of combos that can be formed from the current items in the cart. You do not need to maximize the total discount or the number of combos applied.
2. Apply the resulting discount(s) from the identified combos.
3. Print an updated receipt reflecting these discounts.

Deliverables

• Describe your chosen data structures for tracking item counts in the cart and managing combo definitions.
• Provide pseudocode or actual code for the onUserUpdateSelected function.
• Explain your method for finding any valid combo set (e.g., backtracking, greedy, or another approach that guarantees a valid set if one exists).
• Analyze the time and space complexity of your solution.