function shellsort(array $arr)
{
$n = myCount($arr);
$t = myCeil(myLog($n, 2));
$d = [0, 1];
for ($i = 2; $i <= $t; $i++) {
$d[$i] = 2 * $d[$i - 1] + 1;
}
$d = myArrayReverse($d);
foreach ($d as $curIncrement) {
for ($i = $curIncrement; $i < $n; $i++) {
$x = $arr[$i];
$j = $i - $curIncrement;
while ($j >= 0 && $x < $arr[$j]) {
$arr[$j + $curIncrement] = $arr[$j];
$j = $j - $curIncrement;
}
$arr[$j + $curIncrement] = $x;
}
}
return $arr;
}
function a_star($start, $target, $map)
{
$open_heap = array($start);
// binary min-heap of indexes with values in $f
$open = array($start => TRUE);
// set of indexes
$closed = array();
// set of indexes
$g = [];
$h = [];
$f = [];
$from = [];
$g[$start] = 0;
$h[$start] = heuristic($start, $target);
$f[$start] = $g[$start] + $h[$start];
while ($open) {
$i = heap_pop($open_heap, $f);
//not yet supported
//unset($open[$i]);
$open[$i] = null;
$closed[$i] = TRUE;
if ($i == $target) {
$path = array();
for (; $i != $start; $i = $from[$i]) {
$path[myCount($path)] = $i;
}
return myArrayReverse($path);
}
foreach (neighbors($i, $map) as $j => $step) {
if (!myArrayKeyExists($j, $closed)) {
if (!myArrayKeyExists($j, $open) || $g[$i] + $step < $g[$j]) {
$g[$j] = $g[$i] + $step;
$h[$j] = heuristic($j, $target);
$f[$j] = $g[$j] + $h[$j];
$from[$j] = $i;
if (!myArrayKeyExists($j, $open)) {
$open[$j] = TRUE;
heap_push($open_heap, $f, $j);
} else {
heap_raise($open_heap, $f, $j);
}
}
}
}
}
return FALSE;
}