day 22.php

<?php

class Node
{
    public $left, $right;
    public $data;

    function __construct($data)
    {
        $this->left = $this->right = null;
        $this->data = $data;
    }
}

class Solution
{
    public function insert($root, $data)
    {
        if ($root == null) {
            return new Node($data);
        } else {
            if ($data <= $root->data) {
                $cur = $this->insert($root->left, $data);
                $root->left = $cur;
            } else {
                $cur = $this->insert($root->right, $data);
                $root->right = $cur;
            }
            return $root;
        }
    }

    public function getHeight($root)
    {
        if ($root === null) {
            return -1;
        }

        $leftHeight = $this->getHeight($root->left);
        $rightHeight = $this->getHeight($root->right);

        if ($leftHeight > $rightHeight) {
            $maxHeight = ++$leftHeight;
        } else {
            $maxHeight = ++$rightHeight;
        }

        return $maxHeight;
    }

}//End of Solution
$myTree = new Solution();
$root = null;
$T = intval(fgets(STDIN));
while ($T-- > 0) {
    $data = intval(fgets(STDIN));
    $root = $myTree->insert($root, $data);
}
$height = $myTree->getHeight($root);
echo $height;