11
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White to play (Regular moves apply except for Black King) Black King or Shadow King can move to "any" square that is not attacked by white pieces. It can not capture its opponent. When not in check and there is no unattacked square available, the Shadow King wins. Play the least moves to checkmate the Shadow King.

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    $\begingroup$ This is an excerpt from my old notes. $\endgroup$ – TSLF Oct 8 '16 at 19:50
  • $\begingroup$ Wait, which is Black and which is Shadow? The pieces look to me like they're coloured white and brown. $\endgroup$ – Rand al'Thor Oct 8 '16 at 20:47
  • $\begingroup$ It is the dark brown $\endgroup$ – TSLF Oct 9 '16 at 2:28
  • $\begingroup$ So if at any point there are more than 1 square unattacked on the board, he can basically teleport to any of them right? Does that mean I can decide to which one he goes to build my scenario where he lose is the less possible turns? $\endgroup$ – stack reader Oct 9 '16 at 3:25
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    $\begingroup$ @TSLF I think the problem will sound nicer and clearer if you remove the black king from it. Just "What is the minimal number of moves needed to make, so that each square of the board gets occupied or attacked by some white piece?" $\endgroup$ – Puzzle Prime Oct 9 '16 at 16:12
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OK, I barely made it with 10 moves, but it seems pretty hard to prove this is optimal (and I suspect the answer may be lower). The last move you make is Rh8, which will be the mate.

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    $\begingroup$ There is a difference between "attack all squares" and "checkmate the shadow king". $\endgroup$ – Matsmath Oct 9 '16 at 4:37
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    $\begingroup$ @Matsmath a pretty small difference, tbh... As long as you don't leave the king out of moves before you attack all squares, then it's a mate (and in this case, e7/g7 are always open until the last move, so this is a valid mate) $\endgroup$ – ffao Oct 9 '16 at 4:51
  • $\begingroup$ Correct suspicion and solution. $\endgroup$ – TSLF Oct 9 '16 at 13:34
  • $\begingroup$ @TSLF got down to 10, but since it seems almost impossible to find/prove what is the exact minimum, maybe it is good adding the target number in the description? $\endgroup$ – Puzzle Prime Oct 9 '16 at 14:47
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    $\begingroup$ You can make it 1 move fewer. $\endgroup$ – TSLF Oct 9 '16 at 18:02
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9 moves solution. King and Queen makes 2 moves each,1 move each for other pieces except the unmoved bishop.

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Here is a scenario where I think there are no unattacked squares on the whole map and the king is in check. I will not list all the moves needed cause the list is too long.

EDIT: ok my scenario still has holes...I give up XD

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in case i understood wrong and the king can only move 1 square at a time, since he cannot capture my pieces, all you need is 1 move. Put the queen 1 square up from him.

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    $\begingroup$ Who is attacking a5? $\endgroup$ – ffao Oct 9 '16 at 4:30
  • $\begingroup$ Who is attacking e5? $\endgroup$ – Matsmath Oct 9 '16 at 4:43

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