Design a DS for prices - duplicates allowed

Design a data structure that stores items with associated prices (duplicates allowed) while supporting fast insertion, lookup by price, and sorted as well as range-based retrieval of items.

Naive Approach (ArrayList)

Follow these steps to implement using a simple list:

• Create an Item class with fields name and price.
• Maintain an ArrayList of all items.
• add(price, item) : Append the item to the list.
• find(price): Traverse the list and collect items with the given price.
• printSorted(): Sort the list by price and print all items.
• printGreaterSorted(price): Filter items with price ≥ given price, sort, and print.
• printSmallerSorted(price): Filter items with price < given price, sort, and print.

Implementation

Sorted Data:
Book 50
Notebook 50
Pen 100
Pencil 100
Phone 150
Laptop 200

Items at price 100:
[Pen, Pencil]

Items with price >= 100:
Pen 100
Pencil 100
Phone 150
Laptop 200

Efficient Approach (TreeMap)

Follow these steps to implement the efficient solution:

• Use a TreeMap where the key is the price and the value is a list of items.
• Add items to the list corresponding to their price.
• Retrieve items for a given price directly from the map.
• Iterate over the TreeMap to print items in sorted order.
• Use tailMap() for prices greater than or equal to a value.
• Use headMap() for prices smaller than a value.

Implementation