The randomization of a deck of cards by repeated interleaving. More generally, a shuffle is a rearrangement of the elements in an ordered list.
Shuffling by exactly interleaving two halves of a deck is called a riffle
shuffle. Shuffling by successively interchanging the cards in position 1, 2,
..., with cards in randomly chosen positions
is known as an exchange shuffle. Normal shuffling
leaves gaps of different lengths between the two layers of cards and so randomizes
the order of the cards.
Keller (1995) showed that roughly shuffles are needed just to randomize the bottom card.
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