1 
     left, $ld);23         $right_max = get_max_long($root->right, $rd);24         $depth = max($ld, $rd) + 1;25 26         // echo "{$ld}|{$rd}|{$left_max}|{$right_max}
";27         return max($ld + $rd, max($left_max, $right_max));28     }29 30     #二叉树深度算法31     #此处不用32     function get_depth($root) {33         if (!$root) {34             return 0;35         }36 37         $ld = get_depth($root->left) + 1;38         $rd = get_depth($root->right) + 1;39 40         return max($ld, $rd);41     }42 43     $root = new Node();44     $n1 = new Node();45     $n2 = new Node();46     $n11 = new Node();47     $n12 = new Node();48     $n13 = new Node();49     $n14 = new Node();50     $n15 = new Node();51     $n21 = new Node();52 53     $root->left = $n1;54     $root->right = $n2;55     $n1->left = $n11;56     $n1->right = $n12;57     $n11->left = $n13;58     $n12->right = $n14;59     $n13->left = $n15;60     $n2->right = $n21;61 62     $max = get_max_long($root, $depth);63     echo $max;64 ?>

4 10 3 1 7 11 8 2