CareerCup

Not sure what the hashmap has to do with this, but here's my stab:

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Palindrome {

  static void process(String target) {
    String longest = "";
    for (int i = 0; i < target.length(); i++) {
      String check = target.substring(i);
      for (int pos = 0; pos < (check.length() / 2) + 1; pos++) {
        String part = check.substring(0, pos);
        String regex = part + ".?" + new StringBuilder(part).reverse().toString();
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(check);
        if (matcher.find()) {
          String word = matcher.group();
          if (word.length() > longest.length()) {
            longest = word;
          }
        }
      }
    }
    System.out.println(longest);
  }

  public static void main(String [] args) {
    process("trtrracecaropop");
  }
}

Coupla quick solutions:

n squared:

#!perl -l

use strict;
use warnings;

my @output;

my $y = 0;
my @lines = <DATA>;
for my $line (@lines) {
  chomp $line;
  for my $x (0 .. length ($line) - 1) {
    $output[$y][$x] ||= '-';
    if (substr($line, $x, 1) eq 'x') {
      for my $i (0 .. length ($line) - 1) {
        $output[$y][$i] = 'x';
      }
      for my $i (0 .. $#lines) {
        $output[$i][$x] = 'x';
      }
    }
  }
  $y++;
}

print @$_ for @output;
__DATA__
-----
-----
---x-
x----
-----

Linear:

use strict;
use warnings;

my $y = 0;
my @lines = <DATA>;
my (%x, %y);
for my $line (@lines) {
  chomp $line;
  for my $x (0 .. length ($line)) {
    if (substr($line, $x, 1) eq 'x') {
      $x{$x}++;
      $y{$y}++;
    }
  }
  $y++;
}

for my $i (0 .. @lines - 1) {
  for my $j (0 .. length($lines[0]) - 1) {
    print $y{$i} || $x{$j} ? 'x' : '-';
  }
  print "\n";
}
__DATA__
-----
-----
---x-
x----
-----

Wouldn't you need to sort the keys? Otherwise you're going to be iterating in hash-order.