41 lines
1.1 KiB
Raku
41 lines
1.1 KiB
Raku
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sub solve($hh, $ww, $recurse) {
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my ($h, $w, $t, @grid) = $hh, $ww, 0;
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state $cnt;
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$cnt = 0 if $recurse;
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($t, $w, $h) = ($w, $h, $w) if $h +& 1;
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return 0 if $h == 1;
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return 1 if $w == 1;
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return $h if $w == 2;
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return $w if $h == 2;
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my ($cy, $cx) = ($h, $w) «div» 2;
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my $len = ($h + 1) × ($w + 1);
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@grid[$len--] = 0;
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my @next = -1, -$w-1, 1, $w+1;
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for $cx+1 ..^ $w -> $x {
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$t = $cy × ($w + 1) + $x;
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@grid[$_] = 1 for $t, $len-$t;
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walk($cy - 1, $x);
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}
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sub walk($y, $x) {
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constant @dir = <0 -1 0 1> Z <-1 0 1 0>;
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$cnt += 2 and return if not $y or $y == $h or not $x or $x == $w;
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my $t = $y × ($w+1) + $x;
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@grid[$_]++ for $t, $len-$t;
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walk($y + @dir[$_;0], $x + @dir[$_;1]) if not @grid[$t + @next[$_]] for 0..3;
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@grid[$_]-- for $t, $len-$t;
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}
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$cnt++;
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if $h == $w { $cnt ×= 2 }
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elsif $recurse and not $w +& 1 { solve($w, $h, False) }
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$cnt
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}
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((1..9 X 1..9).grep:{ .[0] ≥ .[1] }).flat.map: -> $y, $x {
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say "$y × $x: " ~ solve $y, $x, True unless $x +& 1 and $y +& 1;
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}
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