A chess puzzle I've seen a while ago

[Ctuchik]

Two chess players are in the middle of a game as one of them accidently knocks the white king off the board. They pick it up, but don't remember where it was standing.
It is black's turn and the board looks like this:

[Chuck]

For the first one, C3.

[Amb]

Second 1, NC6, Black is forced to capture it because it can cause checkmate on its next turn otherwise. This in turn frees the pawn to reach the promotion row

[Amb]

[/rescind due to idiocy]

[Coyote]

For the second problem:

1. Na6
2. Nc7+
3. Nb5
4. Ra8+
5. Ra7
6. Nc7+
7. Na6
8. Ra8+
9. Nb8
10. Nc6+
11. Nd8+
12. Nxe6+
13. Ng5#
(Black moves not shown, since all he can do is move the king back and forth between e8 and f7)

I liked this one--it takes quite a bit of work to reach the goal without accidentally stalemating black.

[Ctuchik]

@Chuck: you should also prove/explain your answer!

[Scurra]

For the first one - what the hell? They couldn't remember which square the White King was on?! I mean, I'm a dreadful player but I can generally remember where the pieces are...
_________________
_{still Quiz Olympiad champion. Must get a life.
New definitions: COFFEE - someone who is coughed upon}

[jbvntx*]

1st one: Black pawn on B4, White pawn on C2, White king on B3. Then Black Bishop to D3 puts White King in check. White moves pawn to C4. Black captures pawn en passant, two discovered checks. White king moves to C3, capturing black pawn. Very slick. I thought there must be a mistake for a while.

[Zahariel]

Wow, jbvntx, even with the answer given in the first reply, I couldn't figure it out.

En passant capture is officially the most confusing rule in this entire game. I never realized it could cause a double discovered check. That's just dizzying.

[Zag]

[Scurra]

Fairy nuff.
Mind you, if that had happened, then I'd still have been standing around with the White King in my hand staring at the board in bemusement when the players came back...
_________________
_{still Quiz Olympiad champion. Must get a life.
New definitions: COFFEE - someone who is coughed upon}

[Amb]

I thought en passant had to be used in the first 5 turns of the game?

[ralphmerridew]

No; it has to be used immediately after the other player moves a pawn two squares.

[Sumudu*]

In fact it would be pretty unusual for the chance to come up within the first five moves.

[Courk]

How do you reason all that out in the first one, though?

[groza528]

Courk: It is black's turn and he is in check. White's last move could not have been the bishop because the only way it could possibly move to that spot is from along the same diagonal, meaning black would already have been in check. Therefore, white's last move must have been the king.
The king must have been blocking the check, which means either c2 or b3. The white king could not possibly have been at c2 because it's impossible for the two kings to be adjacent, which means the white king just moved from b3.
b3 is in doublecheck, and neither the black rook nor the black bishop could have moved to reveal the other, which means both attacks must have been blocked by other pieces immediately before b3 came into check. These two pieces must have been captured immediately before the position we see, which means the white king must have taken one of them. However, the white king obviously couldn't capture on b4 or c4 because it would put itself in check. Therefore, one of the two blocking pieces must have moved away from b4/c4 as black's last move, in order to be captured by the king.
So we have two pieces on b4 and c4. On black's last move he had to move one of them away from b4/c4. He also had to capture the other one. The only way black could possibly have captured either b4/c4 without ending his turn on either of those squares is an en passant capture, b4xc4 e.p.
Sorry, a bit lengthy, but hopefully clear.

[Courk]

Perfect, thank you!

[Ctuchik]

Great job! You got everything right!

Here are two more!
I did not invent them, so I hope you don't know them already

How do you get to this position in 4 moves?

[Antrax]

I believe the second one was already posted, but I really like it nonetheless.
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After years of disappointment with get rich quick schemes, I know I'm gonna get rich with this scheme. And quick!

[mith]

I'm pretty sure I've seen the other as well, though maybe not on here (and it's a good one too).

[jbvntx*]

2nd batch 1st problem: White's four moves take the knight from G1 to B8, capturing a Black knight. Black's four moves get the pawn out of the way and move the knight from G8 to B8, capturing the White knight. These are very different from the "mate in x moves" type puzzles. I like them.

[Janko*]

If you like them you should check out Raymond Smullyan's excellent books of retro chess puzzles (Chess Mysteries of Sherlock Holmes/Arabian Knights). If memory serves, the first one in this thread was composed by Smullyan in his youth. Bear in mind that his first book starts off with puzzles like that as an introduction - they get much more challenging!

[Trojan Horse]

2nd batch 2nd problem (I've never seen it before, BTW):

1. Ne6, threatening 2. Qc8#. Only three moves for Black avoid that mate:

1. ... Bf6
2. Qc8+ Bd8
3. Qxd8#

1. ... h6
2. f8=Q+ Kh7
3. Qe4#

1. ... h5
2. Ng5 any
3. f8=Q#

Did I miss anything?

[Scurra]

Oh wow. The answer to the first one of the second set is so obvious it's really hard to see. Very clever.
_________________
_{still Quiz Olympiad champion. Must get a life.
New definitions: COFFEE - someone who is coughed upon}

[Ctuchik]

[fadeblue]

[Trojan Horse]

Indeed.

Someone solve this already. If I keep thinking about this problem, I won't have time to prepare for my classes!

[fadeblue]

If you're really curious, I found the thread it was previously posted in: http://www.greylabyrinth.com/discussion/viewtopic.php?t=12159

lostdummy solved it at the time.

[Zag]

For the 2nd batch, first problem, are you sure it didn't say 5 moves? Anyway, here is my 5 move solution:

1. Nf3 Nh6
2. Nh4 Nf5
3. Nxf5 d5
4. Rg1 Bxf5
5. Rh1 Bc8


Whenever I think I have 'proof' that something can't be solved, I always end up eating my words. But here's my proof that it can't be done in 4:

I am assuming that the white knight takes the black one, and then some other black piece takes the white knight and then returns to its starting position. I'm pretty sure that, if there is a flaw in my reasoning, this assumption is incorrect.

4 moves means a total of 8 half-moves
It takes 5 half-moves for one knight to take another, from their starting positions (when they start on the same column -- it only takes a 4 half-moves for a knight to take the opposite one).
Black must spend on half-move on the pawn.
Black must also spend two half-moves taking the white knight and then returning whatever piece took it to its starting position.
This totals 8 half-moves, so no other moves are possible.

Since 3 of the 4 black half-moves are accounted for, the black knight can only make one move, and the white knight will have to spend 4 moves reaching and taking it. This poses two different problems: First, if the white knight is taking the black one on its 4th turn, then there isn't time left for another black piece to take it and return. Second, there is no place the black knight can reach in only one move which another black piece can reach and return from in two moves.

Or maybe my initial assumption is wrong. Sigh.

[thok*]

[ralphmerridew]

Position 1 in 3 moves:
Nh3 d5
Na3 BxN
Nb1 Bc8

Position 1 in 4 moves:
Nf3 d5
Ne5 Nf6
Nc6 Nd7
NxN NxN

[groza528]

ralphmerridew: Your 3-move solution doesn't account for the absence of the g8 knight.

[Ctuchik]

Congrats on solving the puzzle

Here's another one:

[Zag]

Got one!

1. e3, Rxe3+
2. c3, Rxc3+
3. Ka2, Ra3+
4. Kb1, Ra1+
5, Kc2, Rc1+
6. Kd3, Rc3+
7. Ke2, Re3+
8. Kf1, Re1+
9. Kg2, Rg1+
10. Kf3, Rxg3+ <-- critical move
11. Ke2, Re3+
12. Kd1, Re1+
13, Kc2, Rc1+
14. Kb3, Rc3+
15. Ka2, Ra3+
16. RxR#

[Zag]

Jeez. I get one of these, and suddenly everyone loses interest in the thread.

[BraveHat]

Nice job, Zag!!

[Johny Fake]

Please excuse me if you've seen this before. (scroll down on the page)

[Zag]

Have you a definitive answer? I'm inclined to say that black wins, but I could pretty easily be convinced.

[Chuck]

Games that allow time travel into the past should have rules covering things like this.

[jesternl]

Futility Closet, where I saw it first, has some great puzzles from time to time. A wonderful waste of time.