二叉树遍历

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

        public function __construct($data){
            $this->data=$data;
        }
    }
    class CreateTree{
        public $tree;
        //二叉树进行插入
        public function insert($data){
            if(!$this->tree){
                $this->tree = new Node($data);
                return ;
            }
            $p = $this->tree;
            while($p){
                if($data < $p->data ){
                    if(!$p->left){
                        $p->left = new Node($data);
                        return ;
                    }
                    $p= $p->left;
                }elseif($data > $p->data){
                    if(!$p->right){
                        $p->right = new Node($data);
                        return;
                    }
                    $p=$p->right;
                }
            }
        }
　　　　//前序遍历
        public function preOrder(){
            $stack = array();
            $root = $this->tree;
            array_push($stack,$root);
            while(!empty($stack)){
                $p = array_pop($stack);
                echo $p->data.PHP_EOL;
                if($p->right != null){
                    array_push($stack,$p->right);
                }
                if($p->left != null){
                    array_push($stack,$p->left);
                }
            }
        }
}
    $objcreate  = new CreateTree();
    $arr = array(33,16,50,13,18,34,58,15,17,25,51,66,19,27,55);
    foreach ($arr as $key => $value) {
        $objcreate->insert($value);
    }
    $objcreate->preOrder();