Online PHP editor | refs for KPDAY

<?php class Nil {} class Leaf { public function __construct(public int $value) {} } class Node { public function __construct(public Tree $left, public Tree $right) {} } class Tree { public function __construct(public Nil|Leaf|Node $val) {} } function depth(Tree $tree): int { $val = $tree->val; return match ($val::class) { Nil::class => 0, Leaf::class => 1, Node::class => 1 + max(depth($val->left), depth($val->right)), }; } $treeExample = new Tree(new Node( new Tree(new Leaf(5)), new Tree(new Node( new Tree(new Node( new Tree(new Nil()), new Tree(new Leaf(2)), )), new Tree(new Nil()), )) )); print depth($treeExample);