本文實例講述了php實現的二叉樹遍歷算法。分享給大家供大家參考，具體如下：

今天使用php來實現二叉樹的遍歷

創建的二叉樹如下圖所示

php代碼如下所示：

<?phphtml' target='_blank'>class Node {  public $value;  public $child_left;  public $child_right;}final class Ergodic {  //前序遍歷:先訪問根節點，再遍歷左子樹，最后遍歷右子樹；并且在遍歷左右子樹時，仍需先遍歷根節點，然后訪問左子樹，最后遍歷右子樹  public static function preOrder($root){    $stack = array();    array_push($stack, $root);    while(!empty($stack)){      $center_node = array_pop($stack);      echo $center_node->value . ' ';      //先把右子樹節點入棧，以確保左子樹節點先出棧      if($center_node->child_right != null) array_push($stack, $center_node->child_right);      if($center_node->child_left != null) array_push($stack, $center_node->child_left);    }  }  //中序遍歷:先遍歷左子樹、然后訪問根節點，最后遍歷右子樹；并且在遍歷左右子樹的時候。仍然是先遍歷左子樹，然后訪問根節點，最后遍歷右子樹  public static function midOrder($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 = $center_node->child_right;    }  }  //后序遍歷:先遍歷左子樹，然后遍歷右子樹，最后訪問根節點；同樣，在遍歷左右子樹的時候同樣要先遍歷左子樹，然后遍歷右子樹，最后訪問根節點  public static function endOrder($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, $center_node);      //左子樹節點先入$pushstack的棧，確保在$visitstack中先出棧      if ($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 $center_node->value . ' ';    }  }}//創建二叉樹$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 = $i;//前序遍歷Ergodic::preOrder($a); //結果是：A B D H I G C E Fecho '<br/>';//中序遍歷Ergodic::midOrder($a); //結果是： H D I B G A E C Fecho '<br/>';//后序遍歷Ergodic::endOrder($a); //結果是: H I D G B E F C A

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