PHP 二叉樹非遞迴遍曆

 1 <?php 2     #二叉樹的非遞迴遍曆 3     class Node { 4         public $data; 5         public $left; 6         public $right; 7     } 8  9     #前序走訪，和深度遍曆一樣10     function preorder($root) {11         $stack = array();12         array_push($stack, $root);13         while (!empty($stack)) {14             $cnode = array_pop($stack);15             echo $cnode->data . " ";16             if ($cnode->right != null) array_push($stack, $cnode->right);17             if ($cnode->left != null) array_push($stack, $cnode->left);18         }19     }20 21     #中序遍曆22     function inorder($root) {23         $stack = array();24         $cnode = $root;25         while (!empty($stack) || $cnode != null) {26             while ($cnode != null) {27                 array_push($stack, $cnode);28                 $cnode = $cnode->left;29             }30 31             $cnode = array_pop($stack);32             echo $cnode->data . " ";33 34             $cnode = $cnode->right;35         }36     }37 38     #後序遍曆39     #使用雙棧實現40     function postorder($root) {41         $pushstack = array();42         $visitstack = array();43         array_push($pushstack, $root);44 45         while (!empty($pushstack)) {46             $cnode = array_pop($pushstack);47             array_push($visitstack, $cnode);48             if ($cnode->left != null) array_push($pushstack, $cnode->left);49             if ($cnode->right != null) array_push($pushstack, $cnode->right);50         }51 52         while (!empty($visitstack)) {53             $cnode = array_pop($visitstack);54             echo $cnode->data . " ";55         }56     }57 58     $root = new Node();59     $n1 = new Node();60     $n11 = new Node();61     $n12 = new Node();62     $n2 = new Node();63     $n21 = new Node();64     $n22 = new Node();65     $root->data = 0;66     $n1->data = 1;67     $n11->data = 11;68     $n12->data = 12;69     $n2->data = 2;70     $n21->data = 21;71     $n22->data = 22;72     $root->left = $n1;73     $root->right = $n2;74     $n1->left = $n11;75     $n1->right = $n12;76     $n2->left = $n21;77     $n2->right = $n22;78 79     preorder($root);80     echo "<br>";81     inorder($root);82     echo "<br>";83     postorder($root);84 ?>