We can just use the shuffle algorithm slightly modified to suit our needs :
use Inline C => <<'END_OF_C_CODE';
void cderange(SV* array_ref) {
AV* array;
I32 index, i;
SV** sv_1, **sv_2;
SV* sv_temp;
if (! SvROK(array_ref))
croak("array_ref is not a reference");
srand(time( NULL ));
array = (AV*)SvRV(array_ref);
index = av_len(array);
for (; index; index--) {
i = (I32) (rand() % (index));
sv_1 = av_fetch(array, index, 0);
sv_2 = av_fetch(array, i, 0);
sv_temp = *sv_1;
*sv_1 = *sv_2;
*sv_2 = sv_temp;
}
return;
}
END_OF_C_CODE
sub derange {
my $first = $_[0];
cderange \@_;
if( $first eq $_[0] ){
($_[0], $_[1]) = ($_[1], $_[0])
}
return @_;
}
This is fast, but don't work very well with very big arrays (size over RANDMAX, usually 32000).
--
Jedaļ
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