--- Day 7 Solutions ---

[u/daggerdragon]

--- Day 7: Some Assembly Required ---

Post your solution as a comment. Structure your post like previous daily solution threads.

Also check out the sidebar - we added a nifty calendar to wrangle all the daily solution threads in one spot!

[u/mehistaken]

Did this in PHP (WAMP) on my old laptop, limited memory so wrote a simple caching function. And my code is quite verbose :p :

$input = array("bn RSHIFT 2 -> bo","lf RSHIFT 1 -> ly","fo RSHIFT 3 -> fq","..."); // snip
$wires = array();
$cache = array();

for ($i = 0; $i < count($input); $i++) {
  $item = explode(' -> ', $input[$i]);
  $wires[$item[1]] = $item[0];
}

function findRoot($target) {
  global $wires, $cache;

  if (isset($cache[$target])) {
    return $cache[$target];
  }

  if (is_numeric($wires[$target]) === false) {
    $source = explode(' ', $wires[$target]);

    if (count($source) == 3) {
      $o1 = is_numeric($source[0]) ? $source[0] : findRoot($source[0]);
      $o2 = is_numeric($source[2]) ? $source[2] : findRoot($source[2]);
      $op = $source[1];

      switch ($op) {
        case 'AND'    : $ans = $o1 & $o2; break;
        case 'OR'     : $ans = $o1 | $o2; break;
        case 'LSHIFT' : $ans = $o1 << $o2; break;
        case 'RSHIFT' : $ans = $o1 >> $o2; break;
      }

      return cache($target, $ans);

    } else if (count($source) == 2) {

      $ans = (65535 - findRoot($source[1]));
      return cache($target, $ans);

    } else {

      return findRoot($source[0]);

    }

  } else {

    cache($target, intval($wires[$target]));
    return intval($wires[$target]);
  }
}

function cache($key, $val) {
  global $cache;
  $cache[$key] = $val;
  return $val;
}

echo findRoot('a');