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pl:prolog:pllib:8_queens_5 [2019/06/27 15:50] |
pl:prolog:pllib:8_queens_5 [2019/06/27 15:50] (aktualna) |
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| + | ====== 8 queens 5 ====== | ||
| + | {{tag>puzzle chess}} | ||
| + | ===== Description ===== | ||
| + | Program solves 8 queens problem | ||
| + | |||
| + | **Source**: PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7. | ||
| + | ===== Download ===== | ||
| + | Program source code: {{prolog:pllib:8_queens_5.pl}} | ||
| + | ===== Listing ===== | ||
| + | <code prolog> | ||
| + | % Figure 4.11 Program 3 for the eight queens problem. | ||
| + | |||
| + | |||
| + | % solution( Ylist) if | ||
| + | % Ylist is a list of Y-coordinates of eight non-attacking queens | ||
| + | |||
| + | solution( Ylist) :- | ||
| + | sol( Ylist, % Y-coordinates of queens | ||
| + | [1,2,3,4,5,6,7,8], % Domain for X-coordinates | ||
| + | [1,2,3,4,5,6,7,8], % Domain for Y-coordinates | ||
| + | [-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7], % Upward diagonals | ||
| + | [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16] ). % Downward diagonals | ||
| + | |||
| + | sol( [], [], Dy, Du, Dv). | ||
| + | |||
| + | sol( [Y | Ylist], [X | Dx1], Dy, Du, Dv) :- | ||
| + | del( Y, Dy, Dy1), % Choose a Y-coordinate | ||
| + | U is X-Y, % Corresponding upward diagonal | ||
| + | del( U, Du, Du1), % Remove it | ||
| + | V is X+Y, % Corresponding downward diagonal | ||
| + | del( V, Dv, Dv1), % Remove it | ||
| + | sol( Ylist, Dx1, Dy1, Du1, Dv1). % Use remaining values | ||
| + | |||
| + | del( Item, [Item | List], List). | ||
| + | |||
| + | del( Item, [First | List], [First | List1] ) :- | ||
| + | del( Item, List, List1). | ||
| + | |||
| + | </code> | ||
| + | ===== Comments ===== | ||
