0832: "Tic-Tac-Toe"

[NeilRashbrook]

Another minor error: the entry for O51647 (i.e. playing X centre, O top left, X right, O left, X bottom left) shows
O#O <- red indicating that you should play here
OX <- missing letter X played on move 3
X##
Same goes for its mirror image.

[Covane]

This has now made me want to see a similar version, except for connect-4.

[Drain]

I know how much work went into this. Excellent work Randall.

[pittaxx]

If you and your opponent knows the tic-tac-toe perfectly, this may be correct. But in real game, there are some other issues to consider:

If you put an X in a corner as your first move, it is almost guaranteed, that your opponent will pick up center (which is optimal move for him and is rather obvious).
But if you pick up center as your first move, most people do not realize, that if they do not pick corner as their next move, they have lost (given that you follow the right moves after). Since half of the moves are corners, and half of the moves are not, that's 50% chance to loose, after X chooses the center (well statistically, in reality it is less, as corner seams somewhat more advantageous even if you don't know the following trick).

I am lazy so I have only shown when the strategy can be put to use (X starts at the center, O does not go into corner) and as far as I know it is the only way to win tic-tac-toe, without your opponent realizing that he has made a mistake.
Moves as follows: black X, black O, red X, red O, blue X. green dots show the next logical moves for O, all of them meaning a loss.



Good luck bullying other people with this strategy, it's rather amusing until they realise what's happening :]

[Alastriona]

How about a game of global thermonuclear war?

[teucer]

How is this NOT a thinly-veiled insult of the intelligence of the readers? He's basically saying "Since you could never figure this out yourself, I compiled this genius chart for you." And yet you still fellate Randall, saying how interesting/useful/whatever it is. I've known that tic-tac-toe was unbeatable with the advantage to the person with the first move since ten years old, at the very latest. It never made sense to my why it was so popular given that fact. Either way, isn't the optimal move always ridiculously obvious?

Of course every adult knows how to always win. But if you represent the answer visually, you get something neat.

[SirMustapha]

Fractal you say? Maybe because that is what it is called.

http://www.stonybrook.edu/philosophy/fractal/2Tic.html

Hah, brilliant, only that that version is a lot worse, because it doesn't have squiggly, poorly drawn lines (who needs rulers?) and is far less prone to mistakes! After all, THAT is what makes xkcd so awesome, innit? Innit?

Next week we'll have another poster bait showcasing Randall's newest brilliant invention: sliced bread.

[chrth]

For the love of God please click one of the links in my sig so I can someday move out of my mom's basement

fixt

[_infina_]

I was testing out a few of these moves and came across two moves that did not have suggested RED Xs. There may be more, but I've pointed arrows to the two Xs that I think should be red at the link below.
http://flarecorp.com/public/forums/tic_tac_toe.png

Watch the red text. It is reserved for mod use.

so, who wants to play a game of Global Thermo-Nuclear War?

[Aarchaput]

I once made an HTML based game of Tic-Tac-Toe. The computer always went first. In all but two cases, the user lost. The user tied in those two cases. I'd post a link, but I don't recall the website it's found on, or even if it can still be found on that website.

[Dauthi]

For the love of God please click one of the links in my sig so I can someday move out of my mom's basement

fixt

<3

I have to say... the perpetual presence of negativity on these boards has finally provoked me into registering just to say:

Really?

You could be living your life, accepting that no one (not even webcomic artists) are perfect and make mistakes and are just people, happy as could be, being thankful that you are occasionally provided with some free entertainment before you get ready to face the day... Instead, you opt to flaunt some meaningless sense of superiority in an effort to condescend to and insult someone you don't know (and hopefully will never meet -- the indignity!). For what? Personal validation? Just because you can?

Even then... why not target the truly deserving? The other people who go out of their way to inject their chosen communities with negativity? At least then you'd be doing some (relative) good while still feeding your inner troll.

TL;DR: Just because you can be an ass on the internet without any RL repercussions doesn't mean you should. If you make the effort to think positively, I think you'd be surprised at how much more you enjoy life. It really won't hurt you at all, I promise.

[jbaber]

I'm glad there's at least the occasional WOPR reference. I can't believe I'm the first person to point out Randall's alt text is incorrect. It should say

A strange game. The only winning move is not to play.

[rwa2]

I'm with pittaxx on this one. X takes center. If O takes a corner, X can always draw. If O takes a middle slot, X can always win. Done in 2 moves.

[konaya]

Colour-blind people who complain about parts of the strip being red: Seriously? Adjust the colour settings on your damn screens. the red-green variety can still see blue, right?

[luftbahnfahrer]

As far as I'm concerned, tic tac toe is such a boring, pointless game that the only winning move really is not to play.


A far, far better game to play with pencil and paper when you are bored with someone is:
http://en.wikipedia.org/wiki/Dots_and_Boxes

Next step: find the optimal strategy for Boxes!

[moth]

This move map is really cool, but it seems to be missing some red ink:

numbering cells
1 2 3
4 5 6
7 8 9
in order of increasing zoom, in the following locations the newest moves are black instead of red:
x583 x567 o127 o1276 o1278 o1279 o351 o3514 o3517 o3518 o594 o749 o7492 o7493 o7496 o983 o9831 o9832 o9834

[jpk]

Well... this is quite strange...

I've spent the last few days programming an AI for Tic Tac Toe. It essentially finds all of the next possible moves, then finds all of the possible moves of all of the previous possible moves, and continues until the recursion ticker reaches 0 (it overloads if I don't) or if someone won and determines the best possible move.

Just to be nitpicky, for me a recursive algorithm that requires a counter is less than fully groovy. Try counting the remaining squares left to play - when available moves is zero, you've bottomed out. Effectively the same thing, but the machine is only looking at the state of the problem, not at any meta-data.
And as someone pointed out, this sounds more like an exhaustive search than an AI. Does the algorithm learn over time and develop strategy?

[SuperfluousFluteMusic]

I like this. This is great.

[uncivlengr]

I think anyone arguing over optimal tic-tac-toe strategies has already lost.

[pointernil]

xkcd is a information representation genius.
Someone please create a zoomable seadragon / google-maps like view of this... "fractals" ftw!

[Vir4030]

Really cool, but a couple mistakes. They've been pointed out.

I've always been fascinated by tic-tac-toe strategy. Yes, it's been quite obvious to me since well before 2007 that tic-tac-toe will always end in a tie unless someone makes a mistake.

[Vnend]

Am I the only one who always looked at tic-tac-toe Ender-style? No matter where the X went, I always mentally oriented it to the top-left or top-middle of the board.

Well, I didn't do that, but I love the technique. Good job, and thanks for pointing that out.

[Diadem]

I didn't like this one. It's so obvious. You can solve tic-tac-toe in half an hour with pen and paper. I'm sure most people here did so when they were ten. The alt-text is awesome, but other than that, this comic just insults our intelligence.

And then played draughts, where oops, person who went first always won if they knew what to do.

Given the game wasn't solved until 2007, and it took twenty years and hundreds of computers to solve, I expect that most eight-year-olds do not play a deep enough game to actually always win if they went first, but merely that the first move was sufficient advantage to beat other eight-year-olds who also lacked a deep game.

You're wrong. Checkers has been solved, draughts has not. Also, checkers is a draw with perfect play, not a forced win.

[meatyochre]

ONLY on xkcd would multiple someones notice and point out an error in a teenily-fractallated bit of didactery.

I'm frankly taken aback that people looked at it that closely. It's a comic, not a how-to guide for losing one's virginity.

[uncivlengr]

ONLY on xkcd would multiple someones notice and point out an error in a teenily-fractallated bit of didactery.

I'm frankly taken aback that people looked at it that closely. It's a comic, not a how-to guide for losing one's virginity.

Instead of Xs and Os, when you zoom in to the tiniest little squares in the middle they should should spell out, "Seriously? It's a webcomic."

[Captain Chaos]

I'm glad there's at least the occasional WOPR reference. I can't believe I'm the first person to point out Randall's alt text is incorrect. It should say

A strange game. The only winning move is not to play.

It's not "incorrect". It's a parody of the line from War Games...

[dougw]

Since Tic-Tac-Toe is so boring to play, take the WOPR route and let this poster play itself. Here's what you get:

Tic-Tac-Toe comic plays itself

[seedy]

When I was bored in school, I invented a variant of Tic-Tac-Toe that made it mildly more interesting.
For a while, anyway.

The goal was to force your opponent to win. So you ended up making all sorts of vague moves to leave your opponent as many options as possible.

As we got the hang of it, it turned out that whoever went first always ended up "losing" (i.e. getting a row/diagonal).
I suppose this would be that whoever goes first always ends up having to fill in the 9th (final) box as long as the
opponent never made any mistakes.

Anyway, give it a try! If nothing else it ends up confusing the hell out of people looking over your shoulder.

[dp2]

I'm not going to bother analyzing this, but I am consistently impressed with Randall's ingenuity in representing things graphically.

[dp2]

I didn't like this one. It's so obvious. You can solve tic-tac-toe in half an hour with pen and paper. I'm sure most people here did so when they were ten. The alt-text is awesome, but other than that, this comic just insults our intelligence.

In comics like this, the take-away for me is the graph itself, not the data.

[Apeiron]

Fractal you say? Maybe because that is what it is called.

http://www.stonybrook.edu/philosophy/fractal/2Tic.html

Hah, brilliant, only that that version is a lot worse, because it doesn't have squiggly, poorly drawn lines (who needs rulers?) and is far less prone to mistakes! After all, THAT is what makes xkcd so awesome, innit? Innit?

Next week we'll have another poster bait showcasing Randall's newest brilliant invention: sliced bread.

Is there some other place you go be stupid?

[Soultaker~]

I am extremely disappointed by the fact that Randall Munroe found this online somewhere (like I did a while ago), blatantly copied it in its entirety, and then made no mention of the original source, but does reap the accolades for "his" ingenuity.

For your reference, this book may have been the original source (though the actual image doesn't load completely for me). The picture is also in The Math Book by Clifford A. Pickover which does credit the other authors. Various images can be found online too, and considering Randall's familiarity with the WWW, I strongly doubt he invented this depiction independently.

I should note that the original picture represented all possible games, not strategies for two players, so the comic is original in that regard (at least as far as I know). The diagram style itself is clearly borrowed.

[squareroot]

Heh, just yesterday I had been trying to come up with a fractal variation on tic-tac-toe... each turn, you could either place and X or an O, or subdivide one square into a 3x3. The winner of that subdivision gets the whole square.

Also, 4D Tic-Tac-Toe FTW. Never found anyone to seriously play with me though. They got confused enough with 3D.

Also+, The bottom-middle of the O section (8 if it was keypad) resembles a (2nd iteration) Hilbert's curve from a distance. Which is funny, since this is on a 3-grid, and the Hilbert curve is on a 2/4-grid.

Also++,

Am I the only one who always looked at tic-tac-toe Ender-style? No matter where the X went, I always mentally oriented it to the top-left or top-middle of the board.

I did that too. After each person had made one move, there was only 12 "real" possible states. And once you've learned where to go for each of those, then usually the rest of the game follows logically.

[from canada]

Fractal you say? Maybe because that is what it is called.

http://www.stonybrook.edu/philosophy/fractal/2Tic.html

So one of the first posts has the same thing randall drew, only 100 times better, and everyone is still too busy sucking his balls to even notice?

[shoo]

Hates being color blind right now. . .

[-adam]

I'm suprised I don't see more mistakes, with the detail he goes into, but I have actually found one.

1 2 3
4 5 6
7 8 9

Using that coordinate grid (zooming in after each election), 3,4,5 is wrong. Its a copy of 3,4,6. The third "O" should be in space 5, not 6.

Nice catch... interesting to see the same problem repeated in 7,2,5. I smell symmetry! =)

Also, the subcharts in 1,2,7 and 9,8,3 on the O's chart is all black. As well as 7,4,9 and 3,6,1.

And, yes, I know no one would notice if I did not just point it out. But from the elaborate work Mr. Creator has done before, I figured he'd like this to be error-free.

Such love. =)

[kensey]

A far, far better game to play with pencil and paper when you are bored with someone is:
http://en.wikipedia.org/wiki/Dots_and_Boxes

No way, that takes way too long to set up unless you happen to have grid-ruled paper handy (I do, but most don't). Try Sprouts:

http://en.wikipedia.org/wiki/Sprouts_(game)

And if you want to play a joke on somebody, after teaching them Sprouts, teach them Brussels Sprouts:

http://en.wikipedia.org/wiki/Sprouts_(game)#Brussels_Sprouts

[jonharson]

For once the alt text is not worthy of a real geek, it should have read: The only winning move is to play by the Nash equilibrium, perfectly, waiting for your opponent to make a mistake..

[uncivlengr]

So one of the first posts has the same thing randall drew, only 100 times better, and everyone is still too busy sucking his balls to even notice?

It's not the same thing at all - one denotes all possible moves, and the other denotes all the winning strategies.


...but you were too busy being an ass to even notice.

[Soultaker~]

A number of people already pointed out that the ingenuity lies in the representation of the data, not the data itself, and that is what they are praising. I don't think Randall deserves credit for the representation, and the optimal strategy of Tic-tac-toe itself is not very interesting.

The comic is still cool, and to each their own and such; I just don't think the comic is as impressively ingenious if you are familiar with the original diagram.