本文实例讲述了php实现的二叉树遍历算法。分享给大家供大家参考，具体如下：

今天使用php来实现二叉树的遍历

创建的二叉树如下图所示

php代码如下所示：

<?phpclass Node {  public $value;  public $child_left;  public $child_right;}final class Ergodic {  //前序遍历:先访问根节点，再遍历左子树，最后遍历右子树；并且在遍历左右子树时，仍需先遍历根节点，然后访问左子树，最后遍历右子树  public static function preOrder($root){    $stack = array();    array_push($stack, $root);    while(!empty($stack)){      $center_node = array_pop($stack);      echo $center_node->value . " ";      //先把右子树节点入栈，以确保左子树节点先出栈      if($center_node->child_right != null) array_push($stack, $center_node->child_right);      if($center_node->child_left != null) array_push($stack, $center_node->child_left);    }  }  //中序遍历:先遍历左子树、然后访问根节点，最后遍历右子树；并且在遍历左右子树的时候。仍然是先遍历左子树，然后访问根节点，最后遍历右子树  public static function midOrder($root){    $stack = array();    $center_node = $root;    while (!empty($stack) || $center_node != null) {      while ($center_node != null) {        array_push($stack, $center_node);        $center_node = $center_node->child_left;      }      $center_node = array_pop($stack);      echo $center_node->value . " ";      $center_node = $center_node->child_right;    }  }  //后序遍历:先遍历左子树，然后遍历右子树，最后访问根节点；同样，在遍历左右子树的时候同样要先遍历左子树，然后遍历右子树，最后访问根节点  public static function endOrder($root){    $push_stack = array();    $visit_stack = array();    array_push($push_stack, $root);    while (!empty($push_stack)) {      $center_node = array_pop($push_stack);      array_push($visit_stack, $center_node);      //左子树节点先入$pushstack的栈，确保在$visitstack中先出栈      if ($center_node->child_left != null) array_push($push_stack, $center_node->child_left);      if ($center_node->child_right != null) array_push($push_stack, $center_node->child_right);    }    while (!empty($visit_stack)) {      $center_node = array_pop($visit_stack);      echo $center_node->value . " ";    }  }}//创建二叉树$a = new Node();$b = new Node();$c = new Node();$d = new Node();$e = new Node();$f = new Node();$g = new Node();$h = new Node();$i = new Node();$a->value = "A";$b->value = "B";$c->value = "C";$d->value = "D";$e->value = "E";$f->value = "F";$g->value = "G";$h->value = "H";$i->value = "I";$a->child_left = $b;$a->child_right = $c;$b->child_left = $d;$b->child_right = $g;$c->child_left = $e;$c->child_right = $f;$d->child_left = $h;$d->child_right = $i;//前序遍历Ergodic::preOrder($a); //结果是：A B D H I G C E Fecho "<br/>";//中序遍历Ergodic::midOrder($a); //结果是： H D I B G A E C Fecho "<br/>";//后序遍历Ergodic::endOrder($a); //结果是: H I D G B E F C A

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