private function removeIn(RedBlackTree $t, $key)
{
if ($this->compare($key, $t->key()) < 0) {
if (!$this->isRed($t->left()) && !$this->isRed($t->left()->left())) {
$t = $this->moveRedLeft($t);
}
$t = new self($t->key(), $t->value(), $t->left()->remove($key), $t->right(), $t->color(), $t->isRoot());
} else {
if ($this->isRed($t->left())) {
$t = $this->rotateRight($t);
}
if ($this->compare($key, $t->key()) === 0 && $t->right()->isEmpty()) {
return self::createEmpty();
}
if (!$this->isRed($t->right()) && !$this->isRed($t->right()->left())) {
$t = $this->moveRedRight($t);
}
if ($this->compare($key, $t->key()) === 0) {
$min = $this->minIn($t->right());
$t = new self($min->key(), $min->value(), $t->left(), $this->removeMinIn($t->right()), $t->color(), $t->isRoot());
} else {
$t = new self($t->key(), $t->value(), $t->left(), $t->right()->remove($key), $t->color(), $t->isRoot());
}
}
return $this->balance($t);
}
