Get Maximum Amount

Problem Overview

• Given n item types with quantity[i], an item's price equals the current remaining items of its type.
• With m customers each buying one item, determine the maximum revenue from selling exactly m items.
• Input: int quantity[n] and integer m; Output: long integer maximum amount; constraints up to 1e5.
• Real-world context: a greedy shopkeeper using dynamic pricing in a store setting.
• From IBM interviews; a common coding interview problem and interview question.