Question

所以我一直在做我的研究，我正在尝试用PHP制作BST功能。我遇到了一些问题，实际上只有一个问题。插入重复值时，它将出错并且程序崩溃。我不确定为什么会这样。我在下面插入了类文件。

<?php
    class Node{
        public $value;
        public $leftChild;
        public $rightChild;

        public function __construct($item){
            $this->value = $item;
            //new nodes are blank
            $this->leftChild = null;
            $this->rightChild = null;
        }

        public function inOrder(){
            if($this->leftChild !== null){
                $this->leftChild->inOrder();
            }
            print $this->value."</br>";
            if($this->rightChild !== null){
                $this->rightChild->inOrder();
            }
        }

        public function preOrder(){
            print $this->value."</br>";
            if($this->leftChild !== null){
                $this->leftChild->preOrder();
            }
            if($this->rightChild !== null){
                $this->rightChild->preOrder();
            }   
        }

        public function postOrder(){
            if($this->leftChild !== null){
                $this->leftChild->postOrder();
            }
            if($this->rightChild !== null){
                $this->rightChild->postOrder();
            }   
            print $this->value."</br>";
        }
    }

    class BinaryTree{
        protected $root; //the root node of the tree

        public function __construct(){
            $this->root = null;
        }

        public function isEmpty(){
            return $this->root === null;
        }

        public function insert($item){
            //check if the tree is empty or if the current node is empty
            if($this->isEmpty()){
                //special case if tree is empty
                $this->root = new Node($item);
            }else{
                //get the first node in the tree and begin the walk through
                $current = $this->root;
                while($current != null){
                    if($item < $current->value){
                        if($current->leftChild !== null){
                            $current = $current->leftChild;
                        }else{
                            $current->leftChild = new Node($item);
                            $current = $current->leftChild;
                        }
                    }elseif($item >= $current->value){
                        if($current->rightChild !== null){
                            $current = $current->rightChild;
                        }else{
                            $current->rightChild = new Node($item);
                            $current = $current->rightChild;
                        }
                    }else{
                        return;
                    }
                    //insert the node somewhere in the tree starting at the root
                }
            }
        }
        public function inOrderTraversal(){
            //dump the tree rooted at "root"
            $this->root->inOrder();
        }       

        public function preOrderTraversal(){
            //dump the tree rooted at "root"
            $this->root->preOrder();
        }

        public function postOrderTraversal(){
            $this->root->postOrder();
        }
    }
?>

这是我用来显示结果的一小段代码

<?php
error_reporting(E_ALL);
    require_once "assets/class/tree.class.php";
?>
<!DOCTYPE html>
<html>
    <head>
        <title></title>
    </head>
    <body>
        <?
            $array = array(1, 3, 2, 3, 4, 3, 2);
            $tree  = new BinaryTree();
            for($i = 0; $i < count($array); $i++){
                $tree->insert($array[$i]);
            }

            print_r($tree->inOrderTraversal());
        ?>
    </body>
</html>

通过我的错误日志进行更多研究时，我发现了这个：

PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 16 bytes) on line 77

Answer 1

我弄清楚了我的错误。发生的事情是，一旦找到值，我就不允许循环爆发。从而创造一个无限循环。通过添加中断，我已经解决了这个错误。

while($current != null){
    if($item < $current->value){
        if($current->leftChild !== null){
            $current = $current->leftChild;
        }else{
            $current->leftChild = new Node($item);
            $current = $current->leftChild;
            break;
        }
    }elseif($item >= $current->value){
        if($current->rightChild !== null){
            $current = $current->rightChild;
        }else{
            $current->rightChild = new Node($item);
            $current = $current->rightChild;
            break;
        }
    }else{
        return;
    }
    //insert the node somewhere in the tree starting at the root
}

PHP二进制搜索树重复值错误

1 个答案: