bash and permutations...

masavini · 07-20-2010, 06:16 AM

hi,
i have a (quite short) string with n fields:
gigi;gigi2;gigig;gi;ig;

i need a script to get the best fields combination to let the string match a given length value (best match is equal, then equal-1, then equal-2 and so on)...

i.e.:
if length is 7, the output should be:
gigi;gi
gigi;ig

if length is 6, the output should be:
gigi2

it's quite easy to describe, but i can't really figure out how to put it in a script!
can anybody help me? any hint is welcome...

grail · 07-20-2010, 06:53 AM

Quote:

if length is 7

Length of what ???

masavini · 07-20-2010, 07:23 AM

i guess this code is simple enough to be self-explaining...

Code:

CODES="gigi;gigi2;gigig;gi;ig"

permutations.calculator.sh $CODES > permutations.txt

while read LINE
doLENGTH=${#LINE})
echo $LENGTH";"$LINE >> length.permutations.txtdone < permutations.txt

MAXLENGTH=10

touch fitting.permutations.txt

while [ "$(head -1 fitting.permutations.txt)" == "" ]; doif [ $MAXLENGTH -gt 0 ]; then
grep '^'$MAXLENGTH';' length.permutations.txt > fitting.permutations.txt
let MAXLENGTH=$MAXLENGTH-1
else
echo "no permutations with matching length found" > fitting.permutations.txt
fi
done

how could permutations.calculation.sh look like?

grail · 07-20-2010, 07:48 AM

Well I am guessing you want to generate random chunks of your string so here is a link
about generating random numbers.

masavini · 07-20-2010, 09:39 AM

almost found a solution!

here is a simple perl script for permutations of an array:

Code:

#!/usr/bin/perl

@fillers = ("a","2","3");

permute([@fillers], []);

sub permute {
my @items = @{ $_[0] };
my @perms = @{ $_[1] };
unless (@items) {
 print "@perms\n";
} else {
 my(@newitems,@newperms,$i);
 foreach $i (0 .. $#items) {
  @newitems = @items;
  @newperms = @perms;
  unshift(@newperms, splice(@newitems, $i, 1));
  permute([@newitems], [@newperms]);
 }
}
}

does anybody how can i pass a bash array to this perl script (@fillers)?

MTK358 · 07-20-2010, 11:40 AM

Quote:

Originally Posted by grail

Length of what ???

Quote:

Originally Posted by grail

Well I am guessing you want to generate random chunks of your string so here is a link
about generating random numbers.

AFAIK he wants to find a combination of the given strings that add up to a certain length.

masavini · 07-20-2010, 11:44 AM

Quote:

Originally Posted by MTK358

AFAIK he wants to find a combination of the given strings that add up to a certain length.

exact!

grail · 07-20-2010, 10:34 PM

Quote:

Originally Posted by masavini

Quote:
Originally Posted by MTK358
AFAIK he wants to find a combination of the given strings that add up to a certain length.
exact!

I must not be on the same playing field as you guys then, because this now says to me substring.
If that was the case then it would be as simple as:

Code:

if [[ $length -eq 7 ]]
then
    echo ${str:0:6}
fi

Which I would have guessed is not at all what you were after.

konsolebox · 07-21-2010, 03:33 AM

If grail is right it could be even easier as

Code:

echo "${string:0:length - 1}"

or if length is custom and length < actual_string_length then this can be also applied:

Code:

echo "${string:RANDOM % (actual_string_length - length):length - 1}"