My wife is making a quilt. She has a whole bunch of colors and is making a very simple pattern. I enjoy watching the whole process because it's very mathematical, but it has made me question the four color theorem because I've come up with a counterexample that indicates that I either:
- Do not understand the problem.
- Am missing a solution for this example.
The "counterexample" is this:
++++ +wx+ +yz+ ++++
y are allowed to be the same color you need 5 colors to make this work.
Does adjacency in this problem not include single-point adjacency?