English

Card guessing after an asymmetric riffle shuffle

Combinatorics 2026-02-13 v2 Probability

Abstract

We consider a card guessing game with complete feedback. An ordered deck of nn cards labeled 11 up to nn is riffle-shuffled exactly one time. Given a value p(0,1){12}p\in(0{,}1)\setminus\{\frac12\}, the riffle shuffle is assumed to be unbalanced, such that the cut is expected to happen at position pnp\cdot n. The goal of the game is to maximize the number of correct guesses of the cards: one after another a single card is drawn from the top, and shown to the guesser until no cards remain. We provide a detailed analysis of the optimal guessing strategy and study the distribution of the number of correct guesses.

Keywords

Cite

@article{arxiv.2601.16607,
  title  = {Card guessing after an asymmetric riffle shuffle},
  author = {Markus Kuba},
  journal= {arXiv preprint arXiv:2601.16607},
  year   = {2026}
}

Comments

20 pages, 3 figures. Refernces updated. Extends results of arXiv:2306.16079