JBMO Shortlist 2022 C1
Source: JBMO Shortlist 2022
June 26, 2023
combinatoricsgameJuniorBalkanshortlist
Problem Statement
Anna and Bob, with Anna starting first, alternately color the integers of the set red or blue. At their turn each one can color any uncolored number of they wish with any color they wish. The game ends when all numbers of get colored. Let be the number of pairs , where and are elements of , such that , have the same color, and .
Anna wishes to maximize . What is the maximum value of that she can achieve regardless of how Bob plays?