Eight Queens Puzzle - Sample Program

Sample Program

The following is a Pascal program by Niklaus Wirth. It finds one solution to the eight queens problem.

program eightqueen1(output); var i : integer; q : boolean; a : array of boolean; b : array of boolean; c : array of boolean; x : array of integer; procedure try( i : integer; var q : boolean); var j : integer; begin j := 0; repeat j := j + 1; q := false; if a and b and c then begin x := j; a := false; b := false; c := false; if i < 8 then begin try( i + 1, q); if not q then begin a := true; b := true; c := true; end end else q := true end until q or (j = 8); end; begin for i := 1 to 8 do a := true; for i := 2 to 16 do b := true; for i := -7 to 7 do c := true; try( 1, q); if q then for i := 1 to 8 do write( x:4); writeln end.