game with n circles and k points, one in each circle, circles deleted, min k
Source: Rioplatense Olympiad 2002 level 3 P6
September 6, 2018
combinatoricsgame strategyminimumcombinatorial geometry
Problem Statement
Daniel chooses a positive integer and tells Ana. With this information, Ana chooses a positive integer and tells Daniel. Daniel draws circles on a piece of paper and chooses different points on the condition that each of them belongs to one of the circles he drew. Then he deletes the circles, and only the points marked are visible. From these points, Ana must reconstruct at least one of the circumferences that Daniel drew. Determine which is the lowest value of that allows Ana to achieve her goal regardless of how Daniel chose the circumferences and the points.