Playing Guess Who with Your Kids

Authors Ami Paz, Liat Peterfreund

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Author Details

Ami Paz
  • LISN, CNRS & Paris Saclay University, France
Liat Peterfreund
  • LIGM, CNRS & Gustav Eiffel University, Champs-sur-Marne, France


The authors are grateful to Yonatan, Yuval and Ari for inspiring this work, and to Ben Lee Volk for discussions on error correcting codes.

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Ami Paz and Liat Peterfreund. Playing Guess Who with Your Kids. In 11th International Conference on Fun with Algorithms (FUN 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 226, pp. 23:1-23:10, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


Guess who is a two-player search game in which each player chooses a character from a deck of 24 cards, and has to infer the other player’s character by asking yes-no questions. A simple binary search strategy allows the starting player find the opponent’s character by asking 5 questions only, when the opponent is honest. Real-life observations show that in more realistic scenarios, the game is played against adversaries that do not strictly follow the rules, e.g., kids. Such players might decide to answer all questions at once, answer only part of the questions as they do not know the answers to all, and even lie occasionally. We devise strategies for such scenarios using techniques from error-correcting and erasure codes. This connects to a recent line of work on search problems on graphs and trees with unreliable auxiliary information, and could be of independent interest.

Subject Classification

ACM Subject Classification
  • Theory of computation → Representations of games and their complexity
  • Theory of computation → Sorting and searching
  • Theory of computation → Theory and algorithms for application domains
  • Guess Who?
  • Binary Search
  • Error Correcting Codes
  • Erasure Codes


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