crypt66.php

<?php

$text = <<<EOF

EOF;

$problems = array();
$solutions = array();

preg_match_all('/^(.*)$/m', $text, $problems);

foreach ($problems[0] as $problem) {
  $prefix = convert_to_prefix($problem);
  echo $prefix . PHP_EOL;
  $rprefix = explode(' ', $prefix);
  $solution = rpn(array_reverse($rprefix));
  echo $solution . PHP_EOL;
  $solutions[] = $solution;
}

foreach ($solutions as $solutions) {
  echo chr($solutions);
}

function convert_to_prefix($string) {
  echo $string . PHP_EOL;

  $pnotation = $string;
  $pnotation = preg_replace('/\b3 5\b/', '+', $pnotation);
  $pnotation = preg_replace('/\b3 6\b/', '-', $pnotation);
  $pnotation = preg_replace('/\b3 7\b/', '/', $pnotation);
  $pnotation = preg_replace('/\b1 (\d+)\b/', '$1', $pnotation);
  $pnotation = preg_replace('/\b2 (\d+)\b/', '-$1', $pnotation);

  return $pnotation;
}

// https://gist.github.com/rhrn/3705119
function rpn($params) {

    $count = sizeof($params);

    $result = null;

    $numeric = array();

    for($i = 0; $i < $count; $i++) {

      if (is_numeric($params[$i])) {

        $numeric[] = $params[$i];

      } else {

        switch ($params[$i]) {

          case "+":
            $result = array_pop($numeric) + array_pop($numeric);
            break;
          case "-":
            $result = array_pop($numeric) - array_pop($numeric);
            break;
          case "*":
            $result = array_pop($numeric) * array_pop($numeric);
            break;
          case "/":
            $result = array_pop($numeric) / array_pop($numeric);
            break;

        }
        array_push($numeric, $result);

      }

    }

    return $result;
  }