MathDB
coloring 111^2 points

Source: Rioplatense 1999 L3 P3

September 19, 2022
combinatoricsColoringgamecombinatorial geometry

Problem Statement

Two players AA and BB play the following game: AA chooses a point, with integer coordinates, on the plane and colors it green, then BB chooses 1010 points of integer coordinates, not yet colored, and colors them yellow. The game always continues with the same rules; AA and BB choose one and ten uncolored points and color them green and yellow, respectively. a. The objective of AA is to achieve 1112111^2 green points that are the intersections of 111111 horizontal lines and 111111 vertical lines (parallel to the coordinate axes). BB's goal is to stop him. Determine which of the two players has a strategy that ensures you achieve your goal. b. The objective of AA is to achieve 44 green points that are the vertices of a square with sides parallel to the coordinate axes. BB's goal is to stop him. Determine which of the two players has a strategy that will ensure that they achieve their goal.