Four Colour Theorem The 2019 Stack Overflow Developer Survey Results Are In Announcing the arrival of Valued Associate #679: Cesar Manara Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)Did the Appel/Haken graph colouring (four colour map) proof really not contribute to understanding?How many different game situations has connect four?$Z_n backslash 0$ splits into octetsThe four colour theoremKempe's proof of the four colour theoremChessboard four-colour theoremAlgorithm to solve this grid puzzle?Explain this proof of the 5-color theoremFinding a maximum connected planar graph to prove the four colour theoremStrategies in Memory game

Finding the path in a graph from A to B then back to A with a minimum of shared edges

Typeface like Times New Roman but with "tied" percent sign

Make it rain characters

Is it ok to offer lower paid work as a trial period before negotiating for a full-time job?

Why does the Event Horizon Telescope (EHT) not include telescopes from Africa, Asia or Australia?

Why can't wing-mounted spoilers be used to steepen approaches?

Difference between "generating set" and free product?

Simulating Exploding Dice

How should I replace vector<uint8_t>::const_iterator in an API?

What's the point in a preamp?

Did the UK government pay "millions and millions of dollars" to try to snag Julian Assange?

How to politely respond to generic emails requesting a PhD/job in my lab? Without wasting too much time

Didn't get enough time to take a Coding Test - what to do now?

How does ice melt when immersed in water?

Road tyres vs "Street" tyres for charity ride on MTB Tandem

Take groceries in checked luggage

Why can't devices on different VLANs, but on the same subnet, communicate?

Single author papers against my advisor's will?

How to split my screen on my Macbook Air?

How can I define good in a religion that claims no moral authority?

Is this wall load bearing? Blueprints and photos attached

How did passengers keep warm on sail ships?

Format single node in tikzcd

The following signatures were invalid: EXPKEYSIG 1397BC53640DB551



Four Colour Theorem



The 2019 Stack Overflow Developer Survey Results Are In
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)Did the Appel/Haken graph colouring (four colour map) proof really not contribute to understanding?How many different game situations has connect four?$Z_n backslash 0$ splits into octetsThe four colour theoremKempe's proof of the four colour theoremChessboard four-colour theoremAlgorithm to solve this grid puzzle?Explain this proof of the 5-color theoremFinding a maximum connected planar graph to prove the four colour theoremStrategies in Memory game










7












$begingroup$


I want to colour the US (only the states) map with Yellow, Green, Red and Blue. I was wondering what would be the lowest number of states with the colour of Green. We can of course use the other colours as much as we want. Please note that I want to follow the Four Color Theorem rules.



Motivation:
I am studying graph theory and I want to know if there is a way that we could limit the use of the fourth colour as much as possible. This is not a homework problem.



My attempt:
I have tried many variations and can limit it to 6 and it seems like the
minimum possible but there are infinite possibilities to try so I was wondering if there is a simpler method? Thank you in advance.



Clarification:
I am interested in only the mainland of USA. For states like Michigan that are split, I used the same colour for both parts (since they were not connected directly).










share|cite|improve this question











$endgroup$







  • 1




    $begingroup$
    you would need to agree on a favorite version of the graph. In the actual US, there are islands, states split into disconnected regions, other things forbidden
    $endgroup$
    – Will Jagy
    1 hour ago






  • 1




    $begingroup$
    blog.computationalcomplexity.org/2006/05/… They correctly point out that three colors cannot work, as Nevada has an odd number of neighbors
    $endgroup$
    – Will Jagy
    1 hour ago










  • $begingroup$
    thank you for your suggestion, I made a few clarifications.
    $endgroup$
    – Bor Kari
    41 mins ago















7












$begingroup$


I want to colour the US (only the states) map with Yellow, Green, Red and Blue. I was wondering what would be the lowest number of states with the colour of Green. We can of course use the other colours as much as we want. Please note that I want to follow the Four Color Theorem rules.



Motivation:
I am studying graph theory and I want to know if there is a way that we could limit the use of the fourth colour as much as possible. This is not a homework problem.



My attempt:
I have tried many variations and can limit it to 6 and it seems like the
minimum possible but there are infinite possibilities to try so I was wondering if there is a simpler method? Thank you in advance.



Clarification:
I am interested in only the mainland of USA. For states like Michigan that are split, I used the same colour for both parts (since they were not connected directly).










share|cite|improve this question











$endgroup$







  • 1




    $begingroup$
    you would need to agree on a favorite version of the graph. In the actual US, there are islands, states split into disconnected regions, other things forbidden
    $endgroup$
    – Will Jagy
    1 hour ago






  • 1




    $begingroup$
    blog.computationalcomplexity.org/2006/05/… They correctly point out that three colors cannot work, as Nevada has an odd number of neighbors
    $endgroup$
    – Will Jagy
    1 hour ago










  • $begingroup$
    thank you for your suggestion, I made a few clarifications.
    $endgroup$
    – Bor Kari
    41 mins ago













7












7








7


2



$begingroup$


I want to colour the US (only the states) map with Yellow, Green, Red and Blue. I was wondering what would be the lowest number of states with the colour of Green. We can of course use the other colours as much as we want. Please note that I want to follow the Four Color Theorem rules.



Motivation:
I am studying graph theory and I want to know if there is a way that we could limit the use of the fourth colour as much as possible. This is not a homework problem.



My attempt:
I have tried many variations and can limit it to 6 and it seems like the
minimum possible but there are infinite possibilities to try so I was wondering if there is a simpler method? Thank you in advance.



Clarification:
I am interested in only the mainland of USA. For states like Michigan that are split, I used the same colour for both parts (since they were not connected directly).










share|cite|improve this question











$endgroup$




I want to colour the US (only the states) map with Yellow, Green, Red and Blue. I was wondering what would be the lowest number of states with the colour of Green. We can of course use the other colours as much as we want. Please note that I want to follow the Four Color Theorem rules.



Motivation:
I am studying graph theory and I want to know if there is a way that we could limit the use of the fourth colour as much as possible. This is not a homework problem.



My attempt:
I have tried many variations and can limit it to 6 and it seems like the
minimum possible but there are infinite possibilities to try so I was wondering if there is a simpler method? Thank you in advance.



Clarification:
I am interested in only the mainland of USA. For states like Michigan that are split, I used the same colour for both parts (since they were not connected directly).







graph-theory recreational-mathematics






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited 55 mins ago







Bor Kari

















asked 1 hour ago









Bor KariBor Kari

3749




3749







  • 1




    $begingroup$
    you would need to agree on a favorite version of the graph. In the actual US, there are islands, states split into disconnected regions, other things forbidden
    $endgroup$
    – Will Jagy
    1 hour ago






  • 1




    $begingroup$
    blog.computationalcomplexity.org/2006/05/… They correctly point out that three colors cannot work, as Nevada has an odd number of neighbors
    $endgroup$
    – Will Jagy
    1 hour ago










  • $begingroup$
    thank you for your suggestion, I made a few clarifications.
    $endgroup$
    – Bor Kari
    41 mins ago












  • 1




    $begingroup$
    you would need to agree on a favorite version of the graph. In the actual US, there are islands, states split into disconnected regions, other things forbidden
    $endgroup$
    – Will Jagy
    1 hour ago






  • 1




    $begingroup$
    blog.computationalcomplexity.org/2006/05/… They correctly point out that three colors cannot work, as Nevada has an odd number of neighbors
    $endgroup$
    – Will Jagy
    1 hour ago










  • $begingroup$
    thank you for your suggestion, I made a few clarifications.
    $endgroup$
    – Bor Kari
    41 mins ago







1




1




$begingroup$
you would need to agree on a favorite version of the graph. In the actual US, there are islands, states split into disconnected regions, other things forbidden
$endgroup$
– Will Jagy
1 hour ago




$begingroup$
you would need to agree on a favorite version of the graph. In the actual US, there are islands, states split into disconnected regions, other things forbidden
$endgroup$
– Will Jagy
1 hour ago




1




1




$begingroup$
blog.computationalcomplexity.org/2006/05/… They correctly point out that three colors cannot work, as Nevada has an odd number of neighbors
$endgroup$
– Will Jagy
1 hour ago




$begingroup$
blog.computationalcomplexity.org/2006/05/… They correctly point out that three colors cannot work, as Nevada has an odd number of neighbors
$endgroup$
– Will Jagy
1 hour ago












$begingroup$
thank you for your suggestion, I made a few clarifications.
$endgroup$
– Bor Kari
41 mins ago




$begingroup$
thank you for your suggestion, I made a few clarifications.
$endgroup$
– Bor Kari
41 mins ago










1 Answer
1






active

oldest

votes


















3












$begingroup$

The minimum is two states that use the fourth color. Nevada and its five neighbors cannot be colored with only three colors, and similarly West Virginia and its five neighbors cannot be colored with only three colors.



But if we color Arizona and Ohio a color we use nowhere else, then the remainder of the map can be completed using only three colors:



enter image description here



Adjacencies between the states may be easier to see here.






share|cite|improve this answer











$endgroup$












  • $begingroup$
    I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
    $endgroup$
    – Will Jagy
    20 mins ago










  • $begingroup$
    @WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
    $endgroup$
    – Misha Lavrov
    19 mins ago










  • $begingroup$
    That's pretty good. A simple standard: at least one drivable road between neighbors
    $endgroup$
    – Will Jagy
    15 mins ago











Your Answer








StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "69"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);













draft saved

draft discarded


















StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3186983%2ffour-colour-theorem%23new-answer', 'question_page');

);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









3












$begingroup$

The minimum is two states that use the fourth color. Nevada and its five neighbors cannot be colored with only three colors, and similarly West Virginia and its five neighbors cannot be colored with only three colors.



But if we color Arizona and Ohio a color we use nowhere else, then the remainder of the map can be completed using only three colors:



enter image description here



Adjacencies between the states may be easier to see here.






share|cite|improve this answer











$endgroup$












  • $begingroup$
    I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
    $endgroup$
    – Will Jagy
    20 mins ago










  • $begingroup$
    @WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
    $endgroup$
    – Misha Lavrov
    19 mins ago










  • $begingroup$
    That's pretty good. A simple standard: at least one drivable road between neighbors
    $endgroup$
    – Will Jagy
    15 mins ago















3












$begingroup$

The minimum is two states that use the fourth color. Nevada and its five neighbors cannot be colored with only three colors, and similarly West Virginia and its five neighbors cannot be colored with only three colors.



But if we color Arizona and Ohio a color we use nowhere else, then the remainder of the map can be completed using only three colors:



enter image description here



Adjacencies between the states may be easier to see here.






share|cite|improve this answer











$endgroup$












  • $begingroup$
    I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
    $endgroup$
    – Will Jagy
    20 mins ago










  • $begingroup$
    @WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
    $endgroup$
    – Misha Lavrov
    19 mins ago










  • $begingroup$
    That's pretty good. A simple standard: at least one drivable road between neighbors
    $endgroup$
    – Will Jagy
    15 mins ago













3












3








3





$begingroup$

The minimum is two states that use the fourth color. Nevada and its five neighbors cannot be colored with only three colors, and similarly West Virginia and its five neighbors cannot be colored with only three colors.



But if we color Arizona and Ohio a color we use nowhere else, then the remainder of the map can be completed using only three colors:



enter image description here



Adjacencies between the states may be easier to see here.






share|cite|improve this answer











$endgroup$



The minimum is two states that use the fourth color. Nevada and its five neighbors cannot be colored with only three colors, and similarly West Virginia and its five neighbors cannot be colored with only three colors.



But if we color Arizona and Ohio a color we use nowhere else, then the remainder of the map can be completed using only three colors:



enter image description here



Adjacencies between the states may be easier to see here.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited 11 mins ago

























answered 45 mins ago









Misha LavrovMisha Lavrov

49.3k757108




49.3k757108











  • $begingroup$
    I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
    $endgroup$
    – Will Jagy
    20 mins ago










  • $begingroup$
    @WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
    $endgroup$
    – Misha Lavrov
    19 mins ago










  • $begingroup$
    That's pretty good. A simple standard: at least one drivable road between neighbors
    $endgroup$
    – Will Jagy
    15 mins ago
















  • $begingroup$
    I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
    $endgroup$
    – Will Jagy
    20 mins ago










  • $begingroup$
    @WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
    $endgroup$
    – Misha Lavrov
    19 mins ago










  • $begingroup$
    That's pretty good. A simple standard: at least one drivable road between neighbors
    $endgroup$
    – Will Jagy
    15 mins ago















$begingroup$
I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
$endgroup$
– Will Jagy
20 mins ago




$begingroup$
I need a better atlas. I'm looking at the Philadelphia area, I cannot tell what happens among Pennsylvania, New Jersey, Delaware, Maryland.
$endgroup$
– Will Jagy
20 mins ago












$begingroup$
@WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
$endgroup$
– Misha Lavrov
19 mins ago




$begingroup$
@WillJagy The reference I actually used to color the US was this picture of the US graph, which solves this problem.
$endgroup$
– Misha Lavrov
19 mins ago












$begingroup$
That's pretty good. A simple standard: at least one drivable road between neighbors
$endgroup$
– Will Jagy
15 mins ago




$begingroup$
That's pretty good. A simple standard: at least one drivable road between neighbors
$endgroup$
– Will Jagy
15 mins ago

















draft saved

draft discarded
















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid


  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.

Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3186983%2ffour-colour-theorem%23new-answer', 'question_page');

);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Are there any AGPL-style licences that require source code modifications to be public? Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern) Announcing the arrival of Valued Associate #679: Cesar Manara Unicorn Meta Zoo #1: Why another podcast?Force derivative works to be publicAre there any GPL like licenses for Apple App Store?Do you violate the GPL if you provide source code that cannot be compiled?GPL - is it distribution to use libraries in an appliance loaned to customers?Distributing App for free which uses GPL'ed codeModifications of server software under GPL, with web/CLI interfaceDoes using an AGPLv3-licensed library prevent me from dual-licensing my own source code?Can I publish only select code under GPLv3 from a private project?Is there published precedent regarding the scope of covered work that uses AGPL software?If MIT licensed code links to GPL licensed code what should be the license of the resulting binary program?If I use a public API endpoint that has its source code licensed under AGPL in my app, do I need to disclose my source?

2013 GY136 Descoberta | Órbita | Referências Menu de navegação«List Of Centaurs and Scattered-Disk Objects»«List of Known Trans-Neptunian Objects»

Mortes em março de 2019 Referências Menu de navegação«Zhores Alferov, Nobel de Física bielorrusso, morre aos 88 anos - Ciência»«Fallece Rafael Torija, o bispo emérito de Ciudad Real»«Peter Hurford dies at 88»«Keith Flint, vocalista do The Prodigy, morre aos 49 anos»«Luke Perry, ator de 'Barrados no baile' e 'Riverdale', morre aos 52 anos»«Former Rangers and Scotland captain Eric Caldow dies, aged 84»«Morreu, aos 61 anos, a antiga lenda do wrestling King Kong Bundy»«Fallece el actor y director teatral Abraham Stavans»«In Memoriam Guillaume Faye»«Sidney Sheinberg, a Force Behind Universal and Spielberg, Is Dead at 84»«Carmine Persico, Colombo Crime Family Boss, Is Dead at 85»«Dirigent Michael Gielen gestorben»«Ciclista tricampeã mundial e prata na Rio 2016 é encontrada morta em casa aos 23 anos»«Pagan Community Notes: Raven Grimassi dies, Indianapolis pop-up event cancelled, Circle Sanctuary announces new podcast, and more!»«Hal Blaine, Wrecking Crew Drummer, Dies at 90»«Morre Coutinho, que editou dupla lendária com Pelé no Santos»«Cantor Demétrius, ídolo da Jovem Guarda, morre em SP»«Ex-presidente do Vasco, Eurico Miranda morre no Rio de Janeiro»«Bronze no Mundial de basquete de 1971, Laís Elena morre aos 76 anos»«Diretor de Corridas da F1, Charlie Whiting morre aos 66 anos às vésperas do GP da Austrália»«Morreu o cardeal Danneels, da Bélgica»«Morreu o cartoonista Augusto Cid»«Morreu a atriz Maria Isabel de Lizandra, de "Vale Tudo" e novelas da Tupi»«WS Merwin, prize-winning poet of nature, dies at 91»«Atriz Márcia Real morre em São Paulo aos 88 anos»«Mauritanie: décès de l'ancien président Mohamed Mahmoud ould Louly»«Morreu Dick Dale, o rei da surf guitar e de "Pulp Fiction"»«Falleció Víctor Genes»«João Carlos Marinho, autor de 'O Gênio do Crime', morre em SP»«Legendary Horror Director and SFX Artist John Carl Buechler Dies at 66»«Morre em Salvador a religiosa Makota Valdina»«مرگ بازیکن‌ سابق نساجی بر اثر سقوط سنگ در مازندران»«Domingos Oliveira morre no Rio»«Morre Airton Ravagniani, ex-São Paulo, Fla, Vasco, Grêmio e Sport - Notícias»«Morre o escritor Flavio Moreira da Costa»«Larry Cohen, Writer-Director of 'It's Alive' and 'Hell Up in Harlem,' Dies at 77»«Scott Walker, experimental singer-songwriter, dead at 76»«Joseph Pilato, Day of the Dead Star and Horror Favorite, Dies at 70»«Sheffield United set to pay tribute to legendary goalkeeper Ted Burgin who has died at 91»«Morre Rafael Henzel, sobrevivente de acidente aéreo da Chapecoense»«Morre Valery Bykovsky, um dos primeiros cosmonautas da União Soviética»«Agnès Varda, cineasta da Nouvelle Vague, morre aos 90 anos»«Agnès Varda, cineasta francesa, morre aos 90 anos»«Tania Mallet, James Bond Actress and Helen Mirren's Cousin, Dies at 77»e