FTP, name this theorem that gives the number of shades needed to draw a map.
One person managed to prove the Snark theorem while working on this problem, and one generalization is stated in terms of edge contractions and is named for Hadwiger. Robertson, Sanders, and Seymour improved on the original proof of this problem, while Ringel and Youngs proved a generalized version which relies on the floor function of an expression involving the genus of the surface. Its proof used the method of discharging and defined unavoidable sets and reducible configurations, and it is sometimes called Guthrie's problem. It is a specific case of the Heawood conjecture and was proved by Appel and Hankin using a computer. FTP, name this theorem that gives the number of shades needed to draw a map.
One person managed to prove the Snark theorem while working on this problem, and one generalization is stated in terms of edge contractions and is named for Hadwiger.
{Four color} theorem