## Problem of the Week 1231## Defeating the Four Color TheoremAlice and Bob, moving alternately, will build and color a plane map. It is convenient to use graphs. On her move, Alice adds a vertex V (not on an existing edge) and connects V to one or more existing vertices so that no edges intersect. Bob then assigns V a color different from the color of any of its neighbors. Alice wins if Bob is forced to use a sixth color. Can Alice win? Source: Dave Moran, published at FiveThirtyEight, edited by Oliver Roeder. |

17 November 2016