Open Access
November 1998 No-feedback card guessing for dovetail shuffles
Mihai Ciucu
Ann. Appl. Probab. 8(4): 1251-1269 (November 1998). DOI: 10.1214/aoap/1028903379
Abstract

We consider the following problem. A deck of $2n$ cards labeled consecutively from 1 on top to $2n$ on bottom is face down on the table. The deck is given k dovetail shuffles and placed back on the table, face down. A guesser tries to guess at the cards one at a time, starting from top. The identity of the card guessed at is not revealed, nor is the guesser told whether a particular guess was correct or not. The goal is to maximize the number of correct guesses. We show that, for $k \geq 2 \log_2 (2n) + 1$, the best strategy is to guess card 1 for the first half of the deck and card $2n$ for the second half. This result can be interpreted as indicating that it suffices to perform the order of $\log_2(2n)$ shuffles to obtain a well-mixed deck, a fact proved by Bayer and Diaconis. We also show that if $k = c \log_2 (2n)$ with $1 < c < 2$, then the above guessing strategy is not the best.

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PRINCETON, NEW JERSEY 08540 E-MAIL: ciucu@math.ias.eduPRINCETON, NEW JERSEY 08540 E-MAIL: ciucu@math.ias.edu
Copyright © 1998 Institute of Mathematical Statistics
Mihai Ciucu "No-feedback card guessing for dovetail shuffles," The Annals of Applied Probability 8(4), 1251-1269, (November 1998). https://doi.org/10.1214/aoap/1028903379
Published: November 1998
Vol.8 • No. 4 • November 1998
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