php 二叉树

以下是 PHP 实现二叉树的基本代码：

class TreeNode {
    public $value;
    public $left;
    public $right;

    public function __construct($val) {
        $this->value = $val;
        $this->left = null;
        $this->right = null;
    }
}

class BinaryTree {
    public $root;

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

    public function insert($val) {
        $new_node = new TreeNode($val);
        if ($this->root == null) {
            $this->root = $new_node;
            return;
        }
        $current = $this->root;
        while (true) {
            if ($val < $current->value) {
                if ($current->left == null) {
                    $current->left = $new_node;
                    return;
                } else {
                    $current = $current->left;
                }
            } else {
                if ($current->right == null) {
                    $current->right = $new_node;
                    return;
                } else {
                    $current = $current->right;
                }
            }
        }
    }

    public function search($val) {
        $current = $this->root;
        while ($current != null) {
            if ($val == $current->value) {
                return $current;
            } elseif ($val < $current->value) {
                $current = $current->left;
            } else {
                $current = $current->right;
            }
        }
        return null;
    }

    public function delete($val) {
        $parent = null;
        $current = $this->root;
        $is_left_child = false;
        while ($current != null) {
            if ($val == $current->value) {
                if ($current->left == null && $current->right == null) {
                    if ($current == $this->root) {
                        $this->root = null;
                    } elseif ($is_left_child) {
                        $parent->left = null;
                    } else {
                        $parent->right = null;
                    }
                } elseif ($current->left == null) {
                    if ($current == $this->root) {
                        $this->root = $current->right;
                    } elseif ($is_left_child) {
                        $parent->left = $current->right;
                    } else {
                        $parent->right = $current->right;
                    }
                } elseif ($current->right == null) {
                    if ($current == $this->root) {
                        $this->root = $current->left;
                    } elseif ($is_left_child) {
                        $parent->left = $current->left;
                    } else {
                        $parent->right = $current->left;
                    }
                } else {
                    $successor = $this->get_successor($current);
                    if ($current == $this->root) {
                        $this->root = $successor;
                    } elseif ($is_left_child) {
                        $parent->left = $successor;
                    } else {
                        $parent->right = $successor;
                    }
                    $successor->left = $current->left;
                }
                return;
            } elseif ($val < $current->value) {
                $parent = $current;
                $current = $current->left;
                $is_left_child = true;
            } else {
                $parent = $current;
                $current = $current->right;
                $is_left_child = false;
            }
        }
    }

    public function get_successor($del_node) {
        $successor_parent = $del_node;
        $successor = $del_node;
        $current = $del_node->right;
        while ($current != null) {
            $successor_parent = $successor;
            $successor = $current;
            $current = $current->left;
        }
        if ($successor != $del_node->right) {
            $successor_parent->left = $successor->right;
            $successor->right = $del_node->right;
        }
        return $successor;
    }
}

// 示例用法
$tree = new BinaryTree();
$tree->insert(5);
$tree->insert(3);
$tree->insert(7);
$tree->insert(1);
$tree->insert(4);
$tree->insert(6);
$tree->insert(8);
print_r($tree->search(5)); // 输出: TreeNode Object ( [value] => 5 [left] => TreeNode Object ( [value] => 3 [left] => TreeNode Object ( [value] => 1 [left] => [right] => ) [right] => TreeNode Object ( [value] => 4 [left] => [right] => ) ) [right] => TreeNode Object ( [value] => 7 [left] => TreeNode Object ( [value] => 6 [left] => [right] => ) [right] => TreeNode Object ( [value] => 8 [left] => [right] => ) ) )
$tree->delete(4);
print_r($tree->search(4)); // 输出: null

上面的代码实现了二叉树的基本功能，包括插入节点、查找节点和删除节点。在实际使用时，可根据需要进行修改和扩展。