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A Christmas Chess Puzzle 281

Frederic Friedel writes "Here's a nice little chess puzzle I got from Grandmaster John Nunn many years ago. It looks incredibly simple, but even the strongest players in world have been stumped by it. The problem can be stated in one simple line: A game begins with 1.e4 and ends in the fifth move with knight takes rook mate. What are the moves? If you want to read a couple of stories on it, go to Chessbase. There is a very special prize to be won if you are able to solve it -- a book signed by some of the world's top chess players, testifying that the winner is The Greatest. "

Update: 12/25 11:50 by michael : Well, I thought I figured it out, but I was wrong.

1. e4     b8-c6
2. a4     b4
3. a1-a3  c2
4. a3-d3  b4
5. g7-e2  d3++

Just to clear up some confusion below, the condition is simply that a knight makes the last move of the game, which is a capture of a rook on move five (either color), and this results in checkmate for the other king. Either the knight or some other piece could be giving the check. One poster below reasons that black would be the one giving the checkmate - this is very sound reasoning. :) You just have to think outside the box.

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A Christmas Chess Puzzle

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  • Reminds me of when Chessmaster 6500 beat me in 5 moves when it was set on level novice.

    I'm a REALLY bad chess player.
  • Is there a simple engine that I can download? All you'd need to do is brute-force the possibilities. I might be very wrong, but 5 moves doesn't sound like it would take very long for a fast computer. Just grep through the results for the end move you want.
  • Oops I'm wrong this can be tech-related... see the post before me :-) This post is not off topic, because it is an addendum. Moderators: If a reply to a post has something to do with the original post, can it really be off topic?

  • Ahhh....but, chess is the oldest technology, using the oldest technology.

    Or...something deep n' cheesy like that. Woooo...
  • yeah, this really isn't NEWS because this is an old puzzle, but it's new to most of us. And furthermore, what 'nerd' doesn't play chess??
  • by Bilibala ( 122348 ) on Saturday December 25, 1999 @05:46PM (#1445053)
    Doesn't say if the 5th move is going to be mated by black or white.... guess it'll be easier if it's black mate in 5
  • Damn damn damn. I can do it in *SIX* moves. I try again. :) I'd help if it said who wins. My bets on Black. :)
  • by Rayban ( 13436 ) on Saturday December 25, 1999 @05:50PM (#1445057) Homepage
    Have you ever seen the tree for chess moves? The number of possible board combinations after 5 moves is way, way more than a trillion or so. I wish I could have the number here.

    What I'm curious about, however, is if it could be possible to do some sort of backwards extrapolation. Here's a bit of an idea:

    (8:51pm - restate my assumptions ;))

    1. There are a finite number of squares for a knight to land on in 5 moves.
    2. The rook must be able to make it to one of these squares in 5 moves, so the knight can take it.
    3. The king must be able to make it to a square accessible from one of these squares for a mate to occur.

    Keep in mind these assumptions, as well as the fact that you might be able to castle, and you can reduce your workload dramatically.

    Now... Does the program state that white knight takes black rook, or vice versa?

  • Good God, don't do that. :)

    And its probably more than you think. :)

    But honestly, computers are killing Chess. :( Soon it will be possible to have a computer brute force EVERY SINGLE MOVE in a game and beat a human opponent everytime. Personally, I think this sucks. I'm all for advances in computer science, but Chess is a HUMAN game. It should be played BY HUMANS against one another.

    I'm personally going to work through it, I don't care how long it takes. :)

    I do ask that if you, or anyone else, brute forces the answer, that you don't reveal it or try and win the prize. That's just not fair, really. Actually, I don't care about the prize, but don't spoil the riddle for everyone who wants to work through it -- thats like giving away the ending to a good book/movie, or telling the final score to someone who has taped a sports game. Discovery through diligence is good. Don't kill that, please.

  • All possible chess games out to 5 moves (including both sides) would make cracking DES look like counting to 10.

    Also, the real trick is that the knight must MATE the king, which means that first, the king can't be able to move to a safe space. It either needs to be trapped or all other available spaces need to be guarded. And secondly, the knight can not be captured by any peices from the other side.

  • Yes, I know, chess is the "game of kings" and all... but I've recently learned Go, and no one else seems to play it. Does anyone else on Slashdot play this game?
  • Knight --> fridge --> bourbon --> mate. It can be done in 4.
  • I assume we are talking about Scholar's Mate, which is very similar to Fool's Mate. The two are described on this page [] in some detail.

    The answer, from that page, is "1.e4 e5 2.Bc4 Bc5 3.Qh5 Nf6 4.Qxf7#"
  • 1. e2-e4 | b7-b6
    2. f1-a6 | c8xa6
    3. g1-f3 | g8-f6
    4. g2-g3 | f6-d5
    5. h1-g1 | d5-e3
    6. g1-g2 | e3xg2++

    It's whittling it down to just 5 that's tough.
  • In your solution the last move is made by
    a queen, not a knight as required in a
    puzzle. Also, you only have 4 moves, not 5.
    I suppose, this puzzle is not about the
    quickest mate, but a very specific one.
  • that means ther can only be FOUR more moves after the 1.e4. looks impossible
  • dang, think different for once.

    all you need to fool a computer is a problem that CAN'T be solved with logic. like a riddle. Riddles are solved by defying logic.
  • Uhm, NO. :)

    A game begins with 1.e4 and ends in the fifth move with knight takes rook mate.

    This is the puzzle. KNIGHT TAKES ROOK MATE. That's what makes it hard. There are million ways to mate in 5 moves, but the usual way in which it is done is what makes this hard.

    Please read the summary next time. Alot of people seem to be making this mistake...

  • I've played Go some. When I was going to school at Berkeley, and when there was a lunchtime Go club at a place I worked. Generally though, it's hard to find people to play Go in the US, I agree.

    It's a more forgiving game for people like me who get things right the second time -- usually. :) It's also much, much harder to brute force.
  • what is rook mate and how does a knight take rook mate?
  • Heh, I've been doing it a completly different way. Or rather, ways. I've got half a dozen ways with each black and white. But I can't do it in 5. This is nuts. I might post them later, if someone else doesn't first.

    BTW, thats pretty wack notation :)

  • Let's say a chess game has on average 60 moves by each player, who on average chooses from 10 possibilities. That's 10^120 possible games. Let's say you have a petahertz computer that can evalutate a move per clock. 10^15 moves per second. Let's say every proton in the universe was such a computer and they all worked in parallel. That's 10^80 computers, according to physicist's estimates. Solution time is 10^120 / (10^80 * 10^15) = 10^35 seconds. Since a year only has pi * 10^7 seconds, it would take way over 10^27 years to solve, or about 10^17 times the lifetime of the universe. Chess WILL NEVER be solved by brute force.
  • I once played a chess game that, when you lost, the computer laughed at you...
    And if you won, the board suddenly turned around, so you lost... and the computer laughed...
    At least, I'm -pretty- sure this happened.

    The more I think about it, the less it seems it really happened.

  • No, but I got a Diabolo for Christmas this morning, and I'm making it my new hobby.
  • That means that on the last move, a knight takes opponent's rook, and then it's checkmate.
  • This riddle CAN be solved by a computer:

    There once was a girl from Peru,
    who filled her panties with glue.
    She said with a grin,
    they paid to get in,
    and they'll pay to get out again, too!

    Oh, wait, that's a limerick.

  • For the unenlightened, what is Go?
  • Check out the black bishop dude.
    Nice try though....

  • I'm pretty disappointed that ChessBase couldn't make up their own puzzle at least...
    I'm almost positive I have this puzzle in a book in my house. (but then again, I have a *lot* of chess books ;-) )

    Oh well...

    For those interested, Hugh Courtney's annual Christmas Puzzles in the british magazine "Chess" are especially enteraining ;-)
  • Actually, rumor has it Transmeta is working on subatomic Beowulf clusters.

    Point taken. :)

  • Oops, should have used "preview" -- it's really
    10^7 times the lifetime of the universe to purely brute force chess, with
    a superfast, universe sized, parallel per proton computer.
    Same conclusion, though.
  • True, the tree is huge, but if you have a halfway decent tree pruning algorithm, you could eliminate the vast majority of the tree.

    For example (disclaimer: I'm not a chess person - I hate the game), if the goal is a checkmate in five moves with the knight, then... moving the bishop to one position, and then right back to where it started.. Well, that whole subtree can be killed right off the start. It's obviously (well, unless there's some amazingly subtle chess strategy going on here) a waste of two moves.

    That is how (as far as I am aware) chess games work. they create a tree of moves, and say 'okay, this is the goal..'. Then they prune the tree to lop off the bits that don't show much promise in attaining the goal, and try to brute-force the rest in search of an optimal solution. if it can't find a solution at a given depth in the tree, then it chooses the most 'promising' path, and selects it's move accordingly.

    Correct me if I'm wrong. (Or if this is an insanely outdated technique that modern chess theorists just laugh at).
  • Here [], assuming you only speak English.
  • the knight can take the rook last, but the queen can make the checkmate? if you read the page, at the bottom, the guy who didn't figure it out argued that it wasnt stated properly. ..."When I told him the solution on the phone I could hear Mikhail Botvinnik gasp in the background. And Garry, who was convinced I had stated the problem incorrectly, couldn't believe that he and his students had missed it."...
  • by Anonymous Coward
    Your assumption number 3 is flawed. It never said that the king must be mated BY the knight. In fact, I'll bet that the actual solution involves an "exposed" mate where the knight takes the rook, and exposes another piece, say the queen, that actually "mates" the king.
  • >1. e2-e4 | g7-g6
    >2. g1-e2 | g8-f6
    >3. e2-f4 | h8-g8
    >4. f4-h5 | g8-g7
    >5. h5xg7+++

    Sorry, this doesn't work - black's black bishop
    takes the knight.
  • the knight can take the rook last, but the queen can make the checkmate? like the knight takes the rook and moves out of the way for a queen to make the checkmate. get what im saying?

    if you read the page, at the bottom, the guy who didn't figure it out argued that it wasnt stated properly.

    ..."When I told him the solution on the phone I could hear Mikhail Botvinnik gasp in the background. And Garry, who was convinced I had stated the problem incorrectly, couldn't believe that he and his students had missed it."...
  • Yes, it seems that I missed the crucial bit about the knight. I'll have to work on this one....
  • The world champion Emmanual Lasker said that Go was a superior game to chess.

    - Sam

  • the knight can take the rook last, but the queen can make the checkmate? like the knight takes the rook and moves out of the way for a queen to make the checkmate. get what im saying?

    Discovered check(mate).

  • I assume that the Queen can make the mate, so long as the knight takes the rook. But I haven't found a way to make it work with the Queen in less than 6 moves. :(

    I think I found the solution though. Or, rather, I think I know how to solve. Working on it now. :)

  • Apologies for my lack of knowledge of chess notation...

    h7 - h6 (black king's rook's pawn)
    g1 - f3 (white king's knight)
    g7 - g6 (black king's knight's pawn)
    f3 - e5 (white king's knight)
    f7 - f6 (black king's bishop's pawn)
    e5 - g6 (white king's knight)
    a7 - a6 (black queen's rook's pawn - irrelevant)
    d1 - h5 (white queen)
    a6 - a5 (black queen's rook's pawn - irrelevant)
    g6 - h8 (white king's knight takes rook)

    I think that satisfies all of the requirements.
  • A chess solution may be possible if you consider that most algorithms aimed at this problem are only going to consider reasonable moves and plausible board positions. Kind of like "guided" brute force.

    Checkers on the other hand, - I've read somewhere that there are over 10^120 plausible board positions: orders of magnitude greater than the estimated number of particles in the universe ; )

  • The spoiler that's been posted is not a solution? I won't repeat it here, just in case, but as far as I can see, black checks white at one point, and white never moves out of check. If this is 'thinking outside the box' and this is the actual solution, this puzzle is useless. :) Breaking the rules to solve the puzzle is, in my opinion, cheating. Did I miss something?!
  • It's a very good solution. except that that is White's sixth move, not fifth.
    Michael Sims-michael at
  • Mate is given on whites 6th move, so this isn't a valid solution. Close though. :)
  • You may reduce the workload dramatically, but you still have too much workload for even the most powerful of computers to compute in a reasonable amount of time, because the problem is still not "trivial" (a term my professor used to use to describe easy, ie polynomial or in some cases simply sub exponential time). I have worked on a number of similar problems (ie, given 4 particular pieces, give the one shortest winning sequence). This search tree is incredibly huge unless you utilize some of the heuristic ideas that algorithm genius' (as I call them) have determined to be most efficient for games such as chess, but that still requires that you know how to judge a good chess board, which is sadly something that I suck horribly at. If I remember correctly, the best algorithm I could come up with took approximately 4 minutes on a Pentium II 400, 128M RAM to guarantee the winning moves for a very limited board state. Given that the problem is not a limited state (in that any algorithm still must consider a much larger number of pieces, I dont think we would see a computer calculatable solution for this problem any time in the near future). This is why games such as the chessmaster series make us algorithm design guys drool. [Sn]
  • I must be missing something... maybe the pieces are wrong... I dont understand the letter-number thing... Move the right knight 2 forward and 1 left; 2 right and 1 forward; 2 forward and 1 left; 2 forward and 1 left. Gee that was really easy... could someone tell me how the board is lettered-numbered?
  • From left to right, when sitting on Whites side of the table, is A-H. From the white side to the black side, is 1-8.
    So D1 is Whites Queen.

    When stating a move, the result is sometimes stated by itself, when its obvious what happened.
    (eg: e4, theres only one piece that can make that move, the pawn at e2).

    For more info, check out your local chess faq :)
  • How about:

    1 E2-E4 D7-D6
    2 D1-E2 C8-G4
    3 E2-E3 B8-C6
    4 A2-A3 C6-D4
    5 A3-A4 D4-C2++

    Any problems with this one? The above spoiler does not work as white fails to move out of check at one point.
  • Sorry, but at no point does the knight take the rook, right?

    Rules say: A game begins with 1.e4 and ends in the fifth move with knight takes rook mate..

    You've got Knight takes Pawn mate.

  • >How about:
    >1 E2-E4 D7-D6
    >2 D1-E2 C8-G4
    >3 E2-E3 B8-C6
    >4 A2-A3 C6-D4
    >5 A3-A4 D4-C2++
    >Any problems with this one? The above spoiler >does not work as white fails to move out of check >at one point.

    I believe that a knight must actually take a rook, which invalidates this answer...
  • But it doesn't end with knight takes rook.
    Michael Sims-michael at
  • You have to capture a rook with the last move involving the knight.
  • Whoops. That's what I get for not paying close enough attention... :)
  • by tpck ( 66866 )
    I just had a very disturbing thought.

    What if WHITE Knight takes BLACK Rook, and this causes mate for WHITE? Surely its not that. But it is said: And Garry, who was convinced I had stated the problem incorrectly, couldn't believe that he and his students had missed it.

    If its some silly little trick in the wording, I'm going to be anoyed. Very much so. Grr. Of course, in the meantime, I'm not getting anywhere with this thing. 101 ways to mate in 6, but none in 5. Sigh.

    I'm thinking maybe you need to promote a Pawn? Just a though. Anyone else out there actually working on this?

  • the condition is to take a rook on the last move. you didn't.
  • promoting a pawn? wouldn't that invlove much more than 5 moves?
  • I think you mean: 1. e4 Nc6 2. a4 Nb4 3. Ra3 Nxc2 4. Rd3 Nb4 5. Ne2 Nxd3# Eh?
  • I had this handheld game, double dragon. i sucked real bad at it. once the batteries went bad while i was on a real high level too. i got so pissed off i smashed the fucking thing with a hammer. moral of this story, don't make offtopic troll posts on christmas, unless you have a real low karma like me.
  • your 3rd move. you cannot go from a3-d3 because you are ignoring the check that the knight has on the king.
  • Heh, actually, I've since changed my mind. I just thought it might be black, cuz white is too obvious...
  • you can be moderated to offtopic posting anything. just read some of my posts...
  • I think one of the interesting things about puzzles like this is that you rarely find irrelevant moves. I've seen a few posts here that suggest things like 3. a4 .. 4. a5, ie. just pushing a pawn forward for lack of a better move. Usually in chess puzzles, every move is given for a reason.

    And by the way, check out 1. e4 Nc6 2. a4 Nb4 3. Ra3 Nxc2 4. Rd3 Nb4 5. Ne2 Nxd3# given (albeit slightly incorrectly written) from an Anonymous Coward above.. It looks alright.. ?

  • by tpck ( 66866 )
    But so would everything else... hehe. I dunno, I'm lost. :)
  • whats this 'nice little prize' that guy is tlaking about? for all we know it could be something crappy. im sure someone here can git it right, you just have to think about it. maybe try working backwards or something. but im not gonna try because this confuses me. good luck y'all
  • by Adar ( 33202 ) on Saturday December 25, 1999 @08:19PM (#1445155)
    1. It can't be done with castling (this is fairly obvious- no way to mate with knight at the end.)

    2. The mate is to the king side (the side with no queen- think of the way a knight would have to move...)

    3. It's not a discover mate. That's because b1/b8 to a1/a8 takes at least four moves- which doesn't leave enough time for a relevant queen or bishop move by either side (black must move a pawn.)

    4. The mate does not involve moving any rooks. There are only four positions from which a knight can mate a king on e1/e8; there isn't enough time to move a rook somewhere relevant and make sure it's not protected by any other pieces.

    5. The mate is apparently by black. I say this because, if it's by white, black only has four moves- but a black mate gives black five moves, which should be the least amount you need (assuming e2-e4 is irrelevant- it's a red herring.)

    That's what I was able to figure out...good luck :)

  • by matroid ( 120029 ) on Saturday December 25, 1999 @08:21PM (#1445157) Homepage
    I have discovered a truly marvellous solution to this problem, which however this textbox is not large enough to contain.

    (Now if somebody else actually publishes the solution it will at least be named after me.)

    "He who takes credit for everything, is bound to get credit for something."
    -My Dad
  • Except that's not how moves are counted in chess. A "move" in chess counts both white and black, so a mate in the fifth move could end with either white or black moving:

    1. White Black 2. White Black 3. White Black 4. White Black 5. White


    1. White Black 2. White Black 3. White Black 4. White Black 5. White Black

  • by / ( 33804 ) on Saturday December 25, 1999 @08:29PM (#1445161)
    The king is on e1, so there's no way in heck he can get over to g1. As for e2, that's covered by the bishop on a6. He is truly checkmated, for all the good it does in this contest.
  • E2 - E4 (the starting move required by white)
    D7 - D6 (black queen's pawn)
    F2 - F4 (white king's pawn)
    G8 - F6 (black king's knight)
    E1 - F2 (white king)
    F6 - G4 (black king's knight - check)
    F2 - G3 (white king)
    G4 - F2 (black king's knight)
    G1 - F3 (white king's knight)
    F2 - H1 (black king's knight takes white king's rook - checkmate)
  • Hehe. If you want to locate tech news on Christmas, be my guest.
  • Someone's eventually going to come out and tell us the solution to this, right? I mean, because if not, I may never get another decent night's sleep for the rest of my life...


  • anyone who wants to chat about this or wants to share ideas, come to:

  • So how many slashdotters does it take to screw solve a chess puzzle? Let us take this in steps...

    1. Does it involve MS? If so, 75% of the people will hate the MS led answer, regardless of how it came about.
    2. FreeBSD vs Linux? 10% will get so caught up on what OS Netscape/Lynx/Opera was running on to post the ideas to each other, they will never get anywhere. The MS people are exluded above. Mac users, who uses a mac? (running away)
    3. .005% to the 5 first posters.
    4. 14% will somehow discuss moderation or how checkers and go have similar problems. Thus starting new threads.
    5. The rest .995 will have discussions on topic, but their message threads will be spaced apart by the rest of the banter.

    There was hope..


  • by Our Man In Redmond ( 63094 ) on Saturday December 25, 1999 @09:17PM (#1445187)
    The brief version (for those who don't care to click on the link the previous AC provided):

    Go is a game played worldwide, but has the strongest "community" in the Orient, where there are Go professionals and professional Go commentators and writers (especially in Japan). The rules are fairly simple but unfortunately not simple enough to reproduce here (especially since I'm doing this from memory). Very briefly, it's played on the intersections of a 19x19 grid of lines with pieces called stones. Players alternate placing stones on the grid, attempting to capture as much territory as possible by making it impossible for the opposing player to place uncapturable stones inside the territory. A stone or group of stones is captured if it is completely surrounded by enemy stones, so if a group can't be surrounded it can't be captured. Captured stones count against a player at the end of the game, so efficiency is paramount, both in securing territory and in trying to attack it.

    I remember reading a summary of a book written over 25 years ago comparing chess and go in the context of Eastern vs. Western military philosophy (this was toward the end of the Vietnam war). The author's thesis was that in chess, the object is to capture a particular piece, and a player can sacrifice as many of his pieces as necessary to capture the king. In go, the goal is not to capture particular pieces (in fact, every go stone is just as powerful as every other -- it's how groups of stones are deployed that make them weak or powerful), but to capture territory, and as I mentioned above, the more efficient you are at it, the better go player you'll be,
  • Ever seen the math on the game of Go? Game board is 19x19, black & white players can go more or less anywhere. That gives 350+ possible moves for the first dozen rounds or so. Games tend to last many times longer than that of course. You can do the math yourself.

    As fast as the chess possiblities rise, they are constrained by the possible movements of the pieces, the smaller board size, etc. Go rises orders of magnitude faster, and no computer program has to date (to my knowledge, mostly parrotting things I've skimmed [] here) been able to play even on a beginner's level. Fascinating stuff.

    Not that this helps solve the Fermat's theorem of chess or anything.

  • Well, gnuchess is a Free Software chess program. You can search for it on freshmeat. I am presently working on an optimized brute-force solution to this.
  • A *move* is 1> White Black . What you have said is usually termed as a ply (Ply == 1/2 move)
  • try looking into igs (international go server)
    igs is kindof like a go equivalent of gamespy, except for the fact that it predates gamespy by at least four years ;) clients are available for most platforms, and at any given time there's about a hundred games going on involving everyone from 30 kyu beginners to like 9 dan masters.

    here's their url if you're interested:
  • Last time I checked, this was "News for Nerds", not "Tech News for Nerds".

    Whether you love chess or hate it, you have to admit it's a passtime in which many nerds (and geeks too, for that matter) engage, and is thus "Stuff That Matters" for a large contingent of our colleagues.

    So, in summary, Hemos; you go, girl. Keep posting that chess shit.

    Note to the clueless; Hemo is not female. I am aware of this. Get off the computer and do something else for a while. Watch Springer or something.
  • Yup, I play a bit. No, I'm not good, but I do play it. For a computer player get gnugo (requires CGOBAN IIRC, both oss).
  • 1. e4 f5 2. Ne2 g5 3. Nf4 h5 4. Ng6 a5 5. Qxh5 a4 6. Nxh8#

    Ok, so you see that I've wasted a black move on 4. ...a5.

    Can that move be used to re-position the rook so that this works? I was thinking earlier that the solution had to begin with 1. e4 h5 2. Qxh5 Rxh5, with white's bishop providing the checkmate, but I just don't see how that works, even if black's rook moves to the center....

    Hope this helps.
  • Okay, if I'm thinking "outside the box enough", I think this might satisfy the solution.

    A game begins with 1.e4 and ends in the fifth move with knight takes rook mate.

    That is the problem. Now, it's possible, that with a slight bit of imagination (which I have an abundance of), the sentence could be read as such: "A game begins with 1.e4, and ends in the fifth move with knight taking rook, Mate."

    Just re-read the sentence in your best Aussie impression, and you've got it. Doesn't matter the sequence of moves, long as the fifth move ends in knight taking rook...

    Too far outside the box??? I dunno... Never was all that great at chess...

  • (I know we're not supposed to talk of moderation on slashdot, but, would somebody please moderate Adar's post up? It's about the only interesting one in this whole discussion so far. And would the people who propose ``solutions'' please check them using xboard (run in ``edit game'' mode) before posting them?)

    I agree with these conclusions. And it's infuriating. Castling seemed such an ingenious solution for getting the king and the rook in place; but it just takes too much time. And a discover mate seemed so elegant; but it just doesn't seem to work.

    I also tried the following approach: move the white king's knight to E2 so that the king be completely surrounded by its own pieces, and try to mate from F3 (with the black queen's knight). Ingenious, doesn't it? And as usual, it ``almost'' works; only (1)moving the E2 pawn to E4, (2)getting the white knight in E2, (3) getting the white G pawn out of the way, (4)getting the white H pawn out of the way (so the rook can get out), and (5-6) getting the rook in F3 so the black knight can take it — all that takes 6 moves for white. :-(

    Mating in G2 doesn't seem to work much better. And moving the white king seems to screw everything up.


  • the notation is less whacked, wacky, and wack if it's
    1. e4 | b6
    2. Ba6 | Bxa6
  • For the queen to get involved it takes 2 extraneous moves if you're black, which you just don't have to spend if you're getting the knight over there to claim the rook.

    If you're white, then you can do an uncovered mate in 6 like this, but that doesn't solve the puzzle:
    (white) | (black)
    1. e2-e4 | g7-g5
    2. d1-h5 | a7-a6
    3. g1-f3 | b7-b6
    4. f3-e5 | c7-c6
    5. e5xf7 | c6-c5
    6. f7xh8++
  • Look at all the pieces on the board. For there to be a stalemate, all of one player's pieces can't move. It just can't happen after 5 moves.
  • by Anonymous Coward
    1. e4 | Nf6
    2. f3 | Nxe4
    3. Qe2 | Ng3
    4. Qxe7+ | Qxe7+
    5. Kf2 | NxF1#
  • If yours is the solution, then it's because the English language is ambiguous when it comes to the word "with": either it means "by means of" (in which case your solution fails) or it means "accompanied by" (in which case your solution succeeds, although perhaps comment #145 [] is better in that the knight-takes-rook move also occurs during the 5th move).

    I suspect it's not supposed to be a word-play like that, though, because there are several possible solutions that make use of that trick, and this puzzle probably only has one brilliant solution. But maybe I have too much faith in John Nunn.
  • Correct Solution is 1. e4 | Nf6 2. f3 | Nxe4 3. Qe2 | Ng3 4. Qxe7+ | Qxe7+ 5. Kf2 | NxF1# "make my taco salads pretty, jimmy!" - ucb
  • This was posted earlier by Spicy Biscuit. I'm just writing it down in a different format for those who prefer it:

    1. e2-e4 g8-f6
    2. f2-f3 f6-e4
    3. d1-e2 e4-g3
    4. e2-e7 d8-e7
    5. e1-f2 g3-h1++

    Very ingenious solution :)
  • (Frederic: creating a Slashdot account takes only a few seconds. All you need is to remember a password.)

    If we have by the end of February, I say we can brute force this. There are only eight or nine unknown plies; if we assume that there are around 20 possible moves per ply, which I think is a reasonable order of magnitude (``reasonable'' logarithmically, of course), this makes 500 billion combinations, and at a very very reasonable rate of 10^5 positions analyzed per second (a quite conservative estimate: most engines will do better than that on a modern computer, and they are evaluating, not just checking for mate) this takes 60 days. Put in two or three computers full time for two weeks and we have the answer for sure. And probably much before that, since we know, for example, that the eighth or ninth ply has to be ``knight takes rook''.

    Does anyone know enough about the internals of either crafty or (the new 5.00) GNU chess so that we can extract their movegen and set them running? From the cursory glance I gave them, the source looks like a horribly tangled mess (less so in GNU chess than in crafty, but still rather unappealing).

    Still, it would be more satisfactory to solve it ourselves. ``When you have eliminated the impossible, Watson,'' said Holmes, ``whatever remains, however improbable, must be the solution.''

  • nicely done!

    what, pray tell, did you use the Ti-82 for?

  • Nope... notice that the black queen invalidates that move. The King is definately trapped there...

  • 13&cid=207

    That one 12:04 PM EST, this one 2:15 PM EST.

  • While I understand that you weren't actually responding to my post, just using it as an excuse to toot your own horn and engage in a polemic against people who you don't feel meet your standards for chess skills, I think you're doing a tremendous disservice to the community by discouraging people from exploring.

    If someone makes a post that clearly indicates they're interested in something, but not expert level at it, a much more community-oriented response would be to gently guide them to a greater understanding of the subject.

    I mean, the guy who posted the solution could have insulted *YOU* for not meeting his standards of chess skill.
  • Wow! That takes an incredible amount of stupid play on white's part. Twice, white passes up a pawn for knight exchange, and on move 4, sacrifices the queen for a pawn. The fool's mate is something white can completely miss until it is too late (the first time, of course). This is something else!

  • He used it for the part where he bullshitted you into thinking he didn't just steal it from the anonymous coward who posted [] it earlier.

Things are not as simple as they seems at first. - Edward Thorp