Deck of Cards Shuffling

Problem Overview

• Implement a function to shuffle multiple 52-card decks together using a manual-style shuffle.
• Input: list of Card(suit, rank), with total n cards where n is a multiple of 52; Output: the same cards in shuffled order.
• Constraints: suits in {Hearts, Diamonds, Clubs, Spades}; ranks in {A, 2–10, J, Q, K}.
• Domain: realistic card-deck handling and shuffling simulation.
• From Bloomberg interviews; a coding interview problem often used as an interview question.