Re: Algorithm to convert combinations to bitstring

Misread :(

my %lookup = map { $_ => 1 << (ord($_) - ord('A')) } 'A'..'Z';

my $c = 'ABCHI';

my $bitmap = 0;
$bitmap |= $lookup{$_} for $c =~ /(.)/g;

print('A'..'Z', "\n");
print(scalar(reverse(sprintf("%26b", $bitmap))), "\n");
[download]

~~outputs~~

ABCDEFGHIJKLMNOPQRSTUVWXYZ
111000011
[download]

Update: Array version:

my @powers = map { 1 << $_ } 0..25;

my $c = 'ABCHI';

my $bitmap = 0;
$bitmap |= $powers[ord($_)-ord('A')] for $c =~ /(.)/g;

print('A'..'Z', "\n");
print(scalar(reverse(sprintf("%26b", $bitmap))), "\n");
[download]

Update: Replaced += with |=. It makes it tolerant to repeated letters.

Comment on Re: Algorithm to convert combinations to bitstring Select or Download Code

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Re^2: Algorithm to convert combinations to bitstring by Limbic~Region (Chancellor) on Oct 18, 2006 at 18:41 UTC
ikegami, You will have to forgive me, but I have no idea how this solves the problem I asked. It could very well be that I have not done a good job of explaining what I want but in your example: `N = 26 K = 25 C = 65,780` [download] I do not see how your output tells me that the combination representing 'ABCHI' which should be a single bit in a bitstring of 65,780 bits is present? Cheers - L~R	[reply] [d/l]