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Re^2: Analysing a (binary) string.

by hdb (Monsignor)
on Jun 28, 2013 at 12:23 UTC ( #1041239=note: print w/replies, xml ) Need Help??

in reply to Re: Analysing a (binary) string.
in thread Analysing a (binary) string. (Solved)

I cannot see where you get N factorial from. To me it seems what you describe is N^2. This is also what I get from the brute force method below:

use strict; use warnings; use Time::HiRes qw/time/; sub find_best_offset { my $strref = shift; my $n = length $$strref; my $mindiff = $n; my $best_offset = -1; for( my $i=1; $i<=$n/2; $i++ ) { # shift/rotate string and compare to original my $diff = $$strref ^ substr( $$strref, -$i ).substr( $$strref +, 0, -$i ); # number of differing characters between shifted string and or +iginal my $ndiff = $diff =~ tr/\0//c; # test for and keep optimal solution if( $ndiff < $mindiff ) { return $i unless $ndiff; # best case! $mindiff = $ndiff; $best_offset = $i; } } return $best_offset; } for ( 9, 99, 999, 9999, 99999 ) { my $t = time; my $str1 = "01234567890123456789".("01234567890123456x89" x $_); print find_best_offset( \$str1 ); print "\t$_\t",time-$t,"\n"; }

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