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I don't understand why the Costa Rica example is 3-colorable. The green province in the middle touches 5 other provinces so it seems like it should be 5-colorab
by jscipione 14y ago
I don't understand why the Costa Rica example is 3-colorable. The green province in the middle touches 5 other provinces so it seems like it should be 5-colorable.
- Evbn 14y agoNot all of CRs neighbors touch each other.
- ColinWright 14y agoConsider a pizza sliced into six pieces. Each piece touches only their neighbor on each side, so you can color them alternately red and blue. Now suppose someone carved an island in the middle around an olive that no one wants. That touches all six, but can still be colored green, so we use only three colors in total, despite the middle "region" having six neighbors.