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Graph TheoryChallengeGraph Coloring

Graph Coloring · Challenge problem

Five countries A,B,C,D,EA,B,C,D,E are drawn on a map so that A,B,C,DA,B,C,D all mutually share a border with each other, and EE shares a border only with AA. What is the minimum number of colors needed so that every pair of bordering countries gets different colors?