internet en moins de huit secondes

internet.php

<?php
// INTERNET EN MOINS DE HUIT SECONDES

class decoder
{
  protected
    $code = array(),
    $codeCombinations = array(),
    $operations = array(),
    $operationCombinations = array();

  public function __construct($code, $operations)
  {
    $this->code = $code;
    $this->operations = $operations;
  }

  protected function generateCombinations($begin, $code, $result = array())
  {
    if (count($code) > 0)
    {
      foreach ($code as $i => $item)
      {
        $sliced = $code;
        array_splice($sliced, $i, 1);
        $result = array_merge(
          $result,
          $this->generateCombinations(array_merge($begin, array($item)), $sliced)
        );
      }
    }
    else
    {
      $key = implode('|', $begin);
      $result[$key] = $begin;
    }

    return $result;
  }

  public function generate()
  {
    $this->codeCombinations = $this->generateCombinations(array(), $this->code);
    $this->codeCombinations = array_values($this->codeCombinations);

    foreach ($this->operations as $letter => $operation)
    {
      $this->operationCombinations[$letter] = array_values($this->generateCombinations(array(), $operation));
    }
  }

  protected function test($code, $combination)
  {
    $operation = '';

    foreach ($code as $i => $number)
    {
      $operation .= $number;

      if (isset($combination[$i]))
      {
        $operation .= ' '.$combination[$i].' ';
      }
    }

    $operation = '$result = ('.$operation.');';
    eval($operation);
    return (24 === $result);
  }

  public function testCombinations($operations = array())
  {
    $letters = array();

    foreach ($this->codeCombinations as $code)
    {
      foreach ($this->operationCombinations as $letter => $combinations)
      {
        foreach ($combinations as $combination)
        {
          if ($this->test($code, $combination))
          {
            $letters[] = $letter;
          }
        }
      }
    }

    $letters = array_unique($letters);
    sort($letters);
    var_dump(implode(' ', $letters));
  }
}

$codes = array(
  array(6,6,6,9),
  array(5,5,9,9),
  array(4,5,10,11),
  array(10,12,12,12),
  array(1,1,13,13),
  array(2,8,9,12),
  array(4,4,7,13),
  array(2,5,7,9),
  array(3,5,12,12),
  array(3,8,8,12),
  array(8,8,12,13),
  array(4,7,8,10),
  array(4,5,10,12),
  array(4,4,5,5),
  array(1,1,2,11),
  array(3,3,3,5),
  array(2,3,5,6),
  array(2,3,12,12),
  array(11,12,13,13),
  array(3,4,5,10),
  array(5,9,10,11),
  array(3,3,5,10),
  array(2,5,8,8),
  array(2,2,2,3),
  array(2,5,6,9),
  array(3,9,9,11),
  array(2,2,5,7),
  array(3,3,3,11),
  array(2,5,7,7),
);

$operations = array(
  'B' => array('*', '+', '-'),
  'C' => array('*', '*', '*'),
  'D' => array('*', '*', '+'),
  'E' => array('*', '*', '-'),
  'F' => array('+', '+', '+'),
  'G' => array('+', '+', '-'),
  'H' => array('*', '/', '/'),
  'I' => array('*', '*', '/'),
  'J' => array('/', '/', '+'),
  'K' => array('-', '-', '-'),
  'L' => array('/', '-', '-'),
  'M' => array('/', '+', '-'),
  'N' => array('*', '/', '-'),
  'O' => array('*', '/', '+'),
  'P' => array('/', '/', '-'),
  'Q' => array('/', '/', '/'),
  'R' => array('+', '-', '-'),
  'S' => array('*', '+', '+'),
  'T' => array('*', '-', '-'),
  'U' => array('/', '+', '+')
);

foreach ($codes as $code)
{
  $decoder = new decoder($code, $operations);
  $decoder->generate();
  $decoder->testCombinations($operations);
}