<?php

class Graph
{
    protected $_len = 0;
    protected $_i = 0;
    protected $_g = array();
    protected $_visited = array();

    public function __construct()
    {
        // $this->_g = array(
        //     array(0, 1, 1, 0, 0, 0),
        //     array(1, 0, 0, 1, 0, 0),
        //     array(1, 0, 0, 1, 1, 1),
        //     array(0, 1, 1, 0, 1, 0),
        //     array(0, 0, 1, 1, 0, 1),
        //     array(0, 0, 1, 0, 1, 0),
        // );

        $this->_g = array(
          'A' => array('B', 'F'),
          'B' => array('A', 'D', 'E'),
          'C' => array('F'),
          'D' => array('B', 'E'),
          'E' => array('B', 'D', 'F'),
          'F' => array('A', 'C', 'E'),
        );

        $this->_len = count($this->_g);

        $this->_initVisited();

        // print_r($this->_visited);exit;
    }

    protected function _initVisited()
    {
        // for ($i = 0; $i < $this->_len; $i++) {
        //     $this->_visited[$i] = 0;
        // }

        foreach ($this->_g as $key => $value) {
            $this->_visited[$key] = 0;
        }
    }

    public function depthFirst($ori, $desti)
    {
        $this->_i++;
        $this->_visited[$ori] = 1;

        foreach($this->_g[$ori] as $val){
            if($val==$desti){
                echo $val;
                exit;
            }else{
                if($this->_visited[$val] == 0){
                    echo $val . "->";
                    $this->depthFirst($val, $desti);
                }
            }
        }

        // echo $ori . "\n";

        // for ($i = 0; $i < $this->_len; $i++) {
        //     if ($this->_g[$vertex][$i] == 1 && !$this->_visited[$i]) {
        //         $this->depthFirst($i);
        //     }
        // }

        // foreach ($this->_g[] as $key => $value) {
        //     if($this->_g[$ori][$key] == ){

        //     }
        // }
    }
}

$g = new Graph();
// 2 0 1 3 4 5
$g->depthFirst('D', 'C');
// echo $this->_i;