June 26, 2017

Emmanuel Preissmann

The problem we are considering is the following. A colorblind player is given a set B={b1,b2,...,bN} of N colored balls. He knows that each ball is colored either red or green, and that there are less green balls (this will be called a Red-green coloring), but he cannot distinguish the two colors. For any two balls he can ask whether they are colored the same. His goal is to determine the set of all green balls of B (and hence the set of all red balls). We study here the case where the Red-green coloring is such that there are at most p green balls, where p is given, and denote by Q(N,p,≤) the minimum integer k such that there exists a method that finds for sure, for any Red-green coloring, the color of each ball of B after at most k (color) comparisons. We extend the cases for which the exact value of Q(N,p,≤) is known and provide lower and upper bounds as well as exact values for Q(N,p,=) (defined similarly as Q(N,p,≤), but for a Red-green coloring with exactly p green balls)