fourcolors

An visual demonstration of the four color theorem / map solver, powered by ProcessingJS.

For more information and a demo see this blog post.

How it works

The algorithm in action:

First, the user draws on the canvas. Once finished, the process could be as follows:

1. Find areas/nodes using flood fill (BFS)
2. Find neighbors/edges using "marginal points" for each area and comparing distances
3. Build inner graph representation
4. Solve graph with Welsh-Powell and if this fails, try backtracking
5. Display results on canvas