function _lcs_pos($ypos) {
$end = $this->lcs;
if ($end == 0 || $ypos > $this->seq[$end]) {
$this->seq[++$this->lcs] = $ypos;
$this->in_seq[$ypos] = 1;
return $this->lcs;
}
$beg = 1;
while ($beg < $end) {
$mid = (int) (($beg + $end) / 2);
if ($ypos > $this->seq[$mid]) {
$beg = $mid + 1;
}
else {
$end = $mid;
}
}
USE_ASSERTS && assert($ypos != $this->seq[$end]);
$this->in_seq[$this->seq[$end]] = FALSE;
$this->seq[$end] = $ypos;
$this->in_seq[$ypos] = 1;
return $end;
}