The pseudocode for DFS looks straightforward. In order to track the sequence of node visits, we need to use a queue, which will track the nodes inside our Tree class. Here is our implementation of Tree class with recursive DFS:
class TreeNode { public $data = NULL; public $children = []; public function __construct(string $data = NULL) { $this->data = $data; } public function addChildren(TreeNode $node) { $this->children[] = $node; } } class Tree { public $root = NULL; public $visited; public function __construct(TreeNode $node) { $this->root = $node; $this->visited = new SplQueue; } public function DFS(TreeNode $node) { $this->visited->enqueue($node); if($node->children){ foreach ($node->children ...
