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19 votes
1 answer
2k views

How many such positions are there? (chess/math checkmate puzzle)

I'm interested in this kind of position: There are only 4 pieces on the board. If Whites goes first, they can checkmate in one move. If Blacks goes first, they can checkmate in one move. For example: ...
Mike's user avatar
  • 293
11 votes
3 answers
2k views

How to solve this puzzle of Martin Gardner?

Martin Gardner mentioned the following "chess" problem in his column, Mathematical Games, for Scientific American (he got it from Smullyan, who learned about it from a high school math ...
Favst's user avatar
  • 221
7 votes
3 answers
1k views

Square Free Position

[FEN ""] For the purposes of this question, a “square” is a set of four occupied cells on the chessboard whose centres form a geometric square. The cell may have any orientation. For ...
TSLF's user avatar
  • 325
4 votes
3 answers
402 views

Knights necessary to mate king on large finite board

How many knights would be necessary to mate opponent's king on large finite boards, like a billion times a billion squares? Are they fast enough to surround the opponent's king in a constant number of ...
hoacin's user avatar
  • 3,286
4 votes
1 answer
165 views

A mobility puzzle

[FEN "8/8/8/8/pp6/kp6/1p6/1K6 w KQkq - 0 1"] This is a well-known position: both sides are stalemated (if it's their move). It's the lightest position with this property. Devise the ...
Hauke Reddmann's user avatar
3 votes
1 answer
188 views

How often can the initial position be repeated under FIDE tournament rules?

Recently a game was played where two GMs swapped kingside and queenside knights and then agreed a draw (and got their just dessert): How often can the starting position be repeated in a game without ...
Hauke Reddmann's user avatar
3 votes
1 answer
144 views

"Every" move in long notation

A move here shall be defined as the FIDE super-long notation of a legal chess move: Sg1-f3, O-O, e5xd6 ep, Da8xg8+, Rd1-d6# and whatnot. I.e. starting square, ending square, capture sign, check sign, ...
Hauke Reddmann's user avatar
3 votes
0 answers
46 views

Maximum saved moves to win caused by zugzwang

For a zugzwang where x>y and: If white has the move, White can force checkmate in x full moves If Black has the move, White can force checkmate in y full moves The score of such a zugzwang is x-y....
Lucenaposition's user avatar
2 votes
2 answers
761 views

How many different knight's tours are there?

How many solutions does the Knight’s Tour puzzle have when the knight first moves from square a1, through all squares (on each square once), and return back to a1? Please give some solutions. Also, ...
Ginger Bread's user avatar