Question

Possible Duplicate:
How to join two substrings in perl

How could I find a substring of a string array which corresponds to user entered index of character?

For example: If there is a string $string = 'MFHYRAKCLAMSCTLPHCAKNDHGCTH';and it get broken into array @string = ( "MFHYRA","KCLAM", "SCTLP", "HCAKNDHGCTH" ) ; now if user enters position of A as 6 and 10, how could two corresponding substrings be searched and joined?

Answer 1

Essentially, what you ask is this: we have a position in the initial string. The string gets split up in substrings. In which of the substrings is the position?

Assume that

@pos = ( 5, 7, 9 ) ;

is the list of positions for which you would like to find the substrings.

my $n = 0 ; # current position

my %results ;
foreach my $ss ( @substrings ) {

  $n += length( $ss ) ;

  foreach my $p ( @pos ) {
    if( ! $results{$p} and $p < $n ) { $results{$p} = $ss ; }
  }

}

foreach my $p ( @pos ) {
  print "Position $p, substring $results{$p}\n" ;
}

Clearly, this code could use some optimalization, for example — no need to loop over the elements of @pos if we already have a substring for them, and we should break the operation after the last element of @pos got its substring, but for a few positions entered for the user this doesn’t really matter.