MathDB
Life-changing troll

Source: Iran MO 3rd round 2023 , Day 2 P2

August 16, 2023
algorithmcombinatorics

Problem Statement

There is nn black points in the plane.We do the following algorithm: Start from any point from those nn points and colour it red. Then connect this point to the nearest black point available and colour this new point red. Then do the same with this point but at any step , but you are never allowed to draw a line which intersects on of the current drawn segments. If you reach an intersection , the algorithm is over. Is it true that for any nn and at any initial position , we can start from a point st in the algorithm , we reach all the points?