Re: longest common substring... almost?

There's a difference between

I'm trying to write a script which generates the longest common substring + 1 character for each line in a file.

and

I'm trying to get the script to return the smallest number of characters to uniquely identify each line.

Assume the following lines:

AA
AB
ABC
ABCDE
[download]

In the first case, the output should be

AA
AB
AB
AB
[download]

In the second case, output should be

AA
AB
ABC
ABCD
[download]

For the first case, this should work:

#!/usr/bin/perl -lw

use strict;

chomp( my @lines = <DATA> );

# find shortest line
my @foo = sort { length $a <=> length $b } @lines;
my $diff = $foo[0];


LINES:
  for (@lines) {
    # the longest common substring can only be as long
    # as the shortest line
    my $line = substr $_, 0, length $diff;
    while( $line ) {
      if ( $line eq $diff ) {
        $diff = $line;
        next LINES;
      }
      else {
        # reduce current line and recent common string by one
        $line = substr $line, 0, -1;
        $diff = substr $diff, 0, -1;
      }
    }
  }

for( @lines ) {
  print substr $_, 0, length( $diff ) + 1;
}

__DATA__
AA
AB
ABC
ABCDE
[download]

-- Frank ('s first post at perlmonks)

Comment on Re: longest common substring... almost? Select or Download Code

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Re: Re: longest common substring... almost? by ambrus (Abbot) on Apr 19, 2004 at 09:03 UTC
Later in the original question: I'm trying to get the script to return the smallest number of characters to uniquely identify each line. This makes clear that the poster wants the second case.	[reply]