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PHP binary tree construction algorithm sample code

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Release： 2023-03-12 18:18:01

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This article mainly introduces examples of binary tree construction algorithm in PHP. The editor thinks it is quite good. Now I will share it with you and give it as a reference. Let’s follow the editor and take a look.

Tree is still very important in the data structure. Here, the binary tree is represented by bracket notation. First write a binary tree node class:

// 二叉树节点
class BTNode {
  public $data;

  public $lchild = NULL;

  public $rchild = NULL;

  public function construct($data) {
    $this->data = $data;
  }
}

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Then construct the binary tree:

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 &#39;(&#39;:
        $top++;
        array_push($stack, $p);
        $k = 1;
        break;
      case &#39;)&#39;:
        array_pop($stack);
        break;
      case &#39;,&#39;:
        $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;
    }
  }
}

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Write a function to print the binary tree here (in-order traversal):

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

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Running result:

Enter a string
"A(B(C,D),G(F))"

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