function Fannkuch($n, $_i, $print)
{
$check = 0;
$perm = array();
$perm1 = array();
$count = array();
$maxFlipsCount = 0;
$m = $n - 1;
$perm1 = range(0, $n - 1);
$r = $n;
if (!$print) {
$perm1[$_i] = $n - 1;
$perm1[$n - 1] = $_i;
}
while (TRUE) {
// write-out the first 30 permutations
if ($print) {
foreach ($perm1 as $v) {
echo $v + 1;
}
echo "\n";
if (++$check >= 30) {
return Fannkuch($n, $_i, FALSE);
}
}
while ($r !== 1) {
$count[$r - 1] = $r--;
}
if ($perm1[0] !== 0 && $perm1[$m] !== $m) {
$perm = $perm1;
$flipsCount = 0;
$k = $perm[0];
do {
$i = 1;
$j = $k - 1;
while ($i < $j) {
$tmp = $perm[$i];
$perm[$i++] = $perm[$j];
$perm[$j--] = $tmp;
}
++$flipsCount;
$tmp = $perm[$k];
$perm[$k] = $k;
} while ($k = $tmp);
if ($flipsCount > $maxFlipsCount) {
$maxFlipsCount = $flipsCount;
}
}
do {
if ($r >= $m) {
return $maxFlipsCount;
}
$perm0 = $perm1[0];
$i = 0;
while ($i < $r) {
$perm1[$i++] = $perm1[$i];
}
$perm1[$r] = $perm0;
if (--$count[$r] > 0) {
break;
}
++$r;
} while (TRUE);
}
}
$p[1] = $p[2];
$p[2] = $t;
$sign = 1;
// Rotate 0<-1 and 0<-1<-2.
for ($i = 2; $i < $n; $i++) {
$sx = $s[$i];
if ($sx != 0) {
$s[$i] = $sx - 1;
break;
}
if ($i == $m) {
return array($sum, $maxflips);
}
// Out of permutations.
$s[$i] = $i;
// Rotate 0<-...<-i+1.
$t = $p[0];
for ($j = 0; $j <= $i; $j++) {
$p[$j] = $p[$j + 1];
}
$p[$i + 1] = $t;
}
}
} while (true);
}
$n = $argv[1];
list($checksum, $pf) = Fannkuch($n);
printf("%d\nPfannkuchen(%d) = %d", $checksum, $n, $pf);
?>
}
if ($flipsCount > $maxFlipsCount) {
$maxFlipsCount = $flipsCount;
for ($i = 0; $i < $n; $i++) {
$maxPerm[$i] = $perm1[$i];
}
}
}
while (TRUE) {
if ($r == $n) {
return $maxFlipsCount;
}
$perm0 = $perm1[0];
$i = 0;
while ($i < $r) {
$j = $i + 1;
$perm1[$i] = $perm1[$j];
$i = $j;
}
$perm1[$r] = $perm0;
$count[$r] = $count[$r] - 1;
if ($count[$r] > 0) {
break;
}
$r++;
}
}
}
$n = $argc == 2 ? $argv[1] : 1;
printf("Pfannkuchen(%d) = %d\n", $n, Fannkuch($n));
