Color Map Color Map
English ES FR RU

In mathematics the four color theorem , or the four color map theorem, states that: when given any separation of a plane into contiguous regions and producing a figure called a map, no more than four colors are required to color the regions of the map so that no two adjacent regions have the same color. Two regions are called adjacent if they share a common boundary that is not a corner, where corners are the points shared by three or more regions. For our model we will use a grid with square cells.

You are given a regional map as a grid (matrix). There are N countries located on this map. Each country has a number from 0 to N-1. Two cells are adjacent if they have a common edge. Each country has one or more cells that are connected. Thus you can move between any cells of the country X just using for this adjacent cells.
Each cell is marked by the number of its designated country.

You should "color" a map with 4 colors. All of the cells comprising one country should be one color. Adjacent cells of various countries should not have the same color.

The result should be represented as a sequence of numbers 1,2,3 or 4. Each element shows the color of its country matching the index. For example, the 0th element shows the color of country 0. So the result should have N elements.

color-map color-map

Input: A map of region as a tuple of tuples with integers.

Output: The color sequence as a tuple/list of integer.


color_map(((0, 0, 0), (0, 1, 1), (0, 0, 2)) # [1, 2, 3] or [2, 3, 1] or ...

How it is used: This is a classic constraint satisfaction problem . The four color theorem was proven in 1976 by Kenneth Appel and Wolfgang Haken. It was the first major theorem to be proved using a computer. Appel and Haken's approach started by showing that there is a particular set of 1,936 maps, each of which cannot be part of a smallest-sized counterexample to the four color theorem.

Precondition: 0 < len(region) ≤ 10
all(0 < len(row) ≤ 10 and len(row) == len(region[0]) for row in region)
One country cells are connected.
Country numbers are sequence from 0 to N-1.

CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

pip3 install checkio_client

Configure your tool

checkio --domain=py config --key=

Sync solutions into your local folder

checkio sync

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

checkio serv -d

Alternatevly, you can install Chrome extension or FF addon

checkio install-plugin
checkio install-plugin --ff
checkio install-plugin --chromium

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

<< <
> >>

Whats Next?

Free accounts will see Best CheckiO solutions with some delay.
Best Solutions will be opened in
Become Awesome and Don't wait
The next stage is ""
Will be activated in
View More Solutions Random Review Solutions Share your own solution
Go to the next mission Back to the list of missions Back to the map