The eight queens puzzle is the problem of placing eight chess queens on an 8x8 chessboard such that none of them are able to capture any other using the standard chess queen's moves.
Thus, a solution requires that no two queens share the same row, column, or diagonal.
This puzzle has 92 solutions, but only 12 of them are unique. The other solutions can be obtained by the unique ones by symmetric operations (reflections and rotations).
It can be easy to find one or more unique solutions, but is very difficult to find them all (without using Google of course :) ).
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