function getSignal($signal)
{
global $paths;
if (is_numeric($signal)) {
return intval($signal);
}
$inst = explode(' ', $paths[$signal]);
if (count($inst) == 1) {
return getSignal($paths[$signal]);
}
if (count($inst) == 2) {
list(, $a) = $inst;
$paths[$signal] = 65535 - getSignal($a);
return $paths[$signal];
}
list($a, $op, $b) = $inst;
$a = getSignal($a);
$b = getSignal($b);
switch ($op) {
case 'AND':
$paths[$signal] = $a & $b;
break;
case 'OR':
$paths[$signal] = $a | $b;
break;
case 'LSHIFT':
$paths[$signal] = $a << $b;
break;
case 'RSHIFT':
$paths[$signal] = $a >> $b;
break;
}
return $paths[$signal];
}
function getSignal($wire)
{
global $wires;
global $instructions;
if (isset($wires[$wire])) {
return $wires[$wire];
}
$chunks = explode(' ', $instructions[$wire]);
if (count($chunks) == 1) {
if (is_numeric($chunks[0])) {
$wires[$wire] = $chunks[0];
} else {
$wires[$wire] = getSignal($chunks[0]);
}
return $wires[$wire];
}
if (count($chunks) == 2) {
$originalSignal = getSignal($chunks[1]);
$wires[$wire] = ~$originalSignal & 0xffff;
return $wires[$wire];
} else {
if (is_numeric($chunks[0])) {
$signal1 = $chunks[0];
} else {
$signal1 = getSignal($chunks[0]);
}
if (is_numeric($chunks[2])) {
$signal2 = $chunks[2];
} else {
$signal2 = getSignal($chunks[2]);
}
switch ($chunks[1]) {
case 'OR':
$wires[$wire] = $signal1 | $signal2;
break;
case 'AND':
$wires[$wire] = $signal1 & $signal2;
break;
case 'LSHIFT':
$wires[$wire] = $signal1 << $signal2;
break;
case 'RSHIFT':
$wires[$wire] = $signal1 >> $signal2;
break;
}
return $wires[$wire];
}
}
function execInstruction($instruction, &$circuit)
{
$exploded = explode(' ', $instruction);
$wire = end($exploded);
switch (count($exploded)) {
case 3:
$signal = getSignal($exploded[0], $circuit);
break;
case 4:
// NOT
$signal = ~getSignal($exploded[1], $circuit) & 65535;
break;
case 5:
$signal1 = getSignal($exploded[0], $circuit);
$signal2 = getSignal($exploded[2], $circuit);
switch ($exploded[1]) {
case 'AND':
$signal = $signal1 & $signal2;
break;
case 'OR':
$signal = $signal1 | $signal2;
break;
case 'LSHIFT':
$signal = $signal1 << $signal2;
break;
case 'RSHIFT':
$signal = $signal1 >> $signal2;
break;
}
break;
}
$circuit[$wire] = $signal;
}
