4a.php

<?php

/**
--- Day 4: High-Entropy Passphrases ---

A new system policy has been put in place that requires all accounts to use a passphrase instead of simply a password. A passphrase consists of a series of words (lowercase letters) separated by spaces.

To ensure security, a valid passphrase must contain no duplicate words.

For example:

    aa bb cc dd ee is valid.
    aa bb cc dd aa is not valid - the word aa appears more than once.
    aa bb cc dd aaa is valid - aa and aaa count as different words.

The system's full passphrase list is available as your puzzle input. How many passphrases are valid?
*/

$input = <<<INPUT
aa bb cc dd
aa bb cc dd aa
aa bb cc dd aaa
INPUT;

$passphrases = explode("\n", $input);
$valid = 0;
foreach ($passphrases as $passphrase) {
  $words = explode(' ', $passphrase);
  $total = count($words);
  $unique = count(array_unique($words));
  if ($total == $unique) {
    $valid++;
  }
}

print $valid . "\n";