29 April 2011

And the story continues ...

I kept on playing with these puzzles I mentioned in the previous post. This stuff is really addictive! Alain had listed some unsolved puzzles which I managed to crack. Weeeeeeeeee! Maybe you want to try one of them yourself?!
  1. Find a position with unique realization after a series of 9 white moves ending with the mate of the black king delivered by a knight. (T. Luffingham)
  2. Find a position with unique realization after a series of 10 white moves ending with the mate of the black king by a double check. (Richard Stanley)
  3. Find a position with unique realization after a series of 10 white moves ending with the mate of the black king by a discovered check but no double check. (Richard Stanley)
There's still one left for which I haven't found the solution, yet. It's by Gianni Donati: Find a position with unique realization after a series of 13 white moves ending with the mate of the black king delivered by a promotion to bishop. Can you help me?

Finally, let's return to problems with the theme that the given move determines all the previous moves. An interesting example is this one for which I also managed to find the missing solution: Find the game that ends with the direct mate 6. Bh7# (Fran├žois Labelle). This is accomplished by the moves 1. e3 g5 2. Qh5 Bg7 3. Qxh7 Nh6 4. Qxh6 0-0 5. Bd3 Bh8 6. Bh7#. If you feed a solving software like Euclide, Natch or Popeye with this position and ask it for the proof game that produces the position after 11 half-moves, its answer might surprise you. The software tells you that the solution is not unique. Hm, what went wrong?! Nothing! This example clearly shows the difference between this type of chess puzzles and the proof games.

In a proof game you start with a final position and there has to be a unique sequence of a given amount of moves to get there. You have no information about any of the moves. On the other hand, this other problem type does not give you the final position but the last move of the game claiming that all the previous moves are uniquely determined thereby. Among all the solutions to the example above that lead to the final position, there's just one (!) that has the move 6. Bh7#, all others end with 6. Bxh7#. Tricky, eh?

These are some easy ones which won't cause much if any headache:
  1. 3. Qxf8+
  2. 3. Qe4+
  3. 3. - Bf6+
  4. 3. - Bxb3+
  5. 3. - Rxe5+
  6. 4. Ra8
  7. 4. - Re2

Solutions:
1 1. Nc3 2. Nd5 3. c3 4. Qc2 5. Qxh7 6. Qxg8 7. Qxg7 8. Qe5 9. Nf6#
2 1. h4 2. Rh3 (or
1. a4 2. Ra3) 3. Rd3 4. Rxd7 5. d4 6. d5 7. d6 8. Qd5 9. Qc6 10. Rxe7
3 1. a4 2. Ra3 3. Rg3 4. b3 5. Bb2 6. Bxg7 7. Bxf8 8. Rxg8 9. Rxh8 10. Bh6 (or 10. Bg7)
4 1. e4 f5 2. Qf3 fxe4 3. Qxf8+
5 1. d4 e5 2. Qd3 exd4 3. Qe4+
6 1. d3 e6 2. Kd2 Be7 3. Kc3 Bf6+
7 1. c3 d6 2. Qb3 Be6 3. Kd1 Bxb3+
8 1. e4 h5 2. Qxh5 Rxh5 3. e5 Rxe5+
9 1. a4 b5 2. axb5 Nc6 3. Rxa7 Rb8 4. Ra8
10 1. e4 h5 2. Qxh5 Rxh5 3. e5 Rxe5+ 4. Kd1 Re2

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