花荣老师的博客

<?PHP
 
$a = intval($_GET['a']);
$b = intval($_GET['b']);
$c = intval($_GET['c']);
$d = intval($_GET['d']);
 
 
print modify_24($a,$b,$c,$d);
function modify_24($aa,$bb,$cc,$dd)
{
        $p = array("aa","bb","cc","dd");
	$op = array('+','-','*','/','-1','1/');
	$ok = false;
	$x = 24;
 
        for($ii=0;$ii<4;$ii++)
        {
                $a = $$p[$ii];
        for($jj=0;$jj<4;$jj++)
        {
                if ($jj==$ii) continue;
                $b = $$p[$jj];
        for($kk=0;$kk<4;$kk++)
        {
                if ($kk == $ii || $kk==$jj) continue;
                $c = $$p[$kk];
        for($ww=0;$ww<4;$ww++)
        {
                if ($ww == $ii || $ww==$kk || $ww==$jj) continue;
                $d = $$p[$ww];
 
		$y_array = array('($x-$a)','($x+$a)','($x/$a)','($x*$a)', '($a-$x)','($a/$x)');
		$r = array();
		for($i=0;$i<6;$i++)
		{
			$y = $y_array[$i];
			$r[0] = $op[$i];
 
			$z_array = array('('.$y.'-$b)','('.$y.'+$b)', '('.$y.'/$b)','('.$y.'*$b)','($b-'.$y.')','($b/'.$y.')');
			for($j=0;$j<6;$j++)
			{
				$z= $z_array[$j];
				$r[1] = $op[$j];
				$zz_array = array($z.'-$c',$z.'+$c',$z.'/$c',$z.'*$c','$c-'.$z,'$c/'.$z);
				for($k=0;$k<6;$k++)
				{
					$zz_str = '$zz='.$zz_array[$k].";";
					eval($zz_str);
					$r[2] = $op[$k];
 
					if (intval($d) ==  strval($zz))
					{
						$ok = true;
						break 7;
					}
				}
			}
		}
 
        }}}}
		//输出：
 
        if ($ok )
        {
                $str = $d;
		$str = a($r[2], $str, $c);
		$str = a($r[1], $str, $b);
		$str = a($r[0], $str, $a);
                return $str."=".$x;
        }
        else
        {
 
                return 'TMD,累死了，算不出来...';
        }
}
 
function a($r, $str, $next)
{
		switch($r)
                {
                        case "-1":
                                $str = "(".$next."-".$str.")";
                                break;
			case "1/":
				$str = $next ." / ".$str;
				break;
                        default:
                                $str = "(".$str .$r.$next.")";
                                break;
                }
		return $str;
}