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81 chars to recursively construct the 2d array (not including "sub f {}"):
sub f { #234567890123456789012345678901234567890123456789012345678901234567890 +12345678901 my$x=my$i=pop;$x?([1..$x],map[(map$_+2*$x-1,reverse@$_),++$i],reverse +f($x-1)):() }
The first argument is the dimension of the spiral.
## print "@$_\n" for f(5); 1 2 3 4 5 16 17 18 19 6 15 24 25 20 7 14 23 22 21 8 13 12 11 10 9
The recursive pattern is the following: An n x n spiral looks like this:
+---------------+ | 1 2 3 ... n | | +-------+ n+1 | | | | . | | | *** | . | | | | . | | +-------+ 2n-1| +---------------+
where the *** box is the (n-1) x (n-1) spiral, rotated 180 degrees and 2n-1 added to each component.

Update: oops, moved a reverse to the right spot (didn't affect char count).

blokhead


In reply to Re: Spiraling integers by blokhead
in thread Spiraling integers by Elijah

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