Map collection

4 April 2022

Title: The United States in four colors
Keywords: #Algorithms #Coloring #Constraints
Author: Philippe Rivière
Date: April 2021

A mathematical theorem demonstrates that four colors are enough to color any map (without two contiguous regions sharing the same color, of course).

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In practice, coloring can be done by hand with patience, or by algorithmic techniques of “logic programming/answer set programming” or “constraint programming”. To compute this map, we used the Clingo solver developed by the University of Potsdam and compiled by Dominik Moritz. Note that some islands remain in gray: since they do not touch any other region, you can assign them any color.

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