PHP构造二叉树算法示例

// 二叉树节点class BTNode {  public $data;  public $lchild = NULL;  public $rchild = NULL;  public function __construct($data) {    $this->data = $data;  }}

function CreateBTNode(&$root,string $str){  $strArr = str_split($str);  $stack = [];  $p = NULL; // 指针  $top = -1;  $k = $j = 0;  $root = NULL;  foreach ($strArr as $ch) {    switch ($ch) {      case '(':        $top++;        array_push($stack, $p);        $k = 1;        break;      case ')':        array_pop($stack);        break;      case ',':        $k = 2;        break;      default:        $p = new BTNode($ch);        if($root == NULL) {          $root = $p;        } else {          switch ($k) {            case 1:              end($stack)->lchild = $p;              break;            case 2:              end($stack)->rchild = $p;              break;          }        }        break;    }  }}

function PrintBTNode($node){  if($node != NULL) {    PrintBTNode($node->lchild);    echo $node->data;    PrintBTNode($node->rchild);  }}