删除main中的int后，BST代码停止工作

#include <iostream>

struct Node {
    int data;
    Node* left;
    Node* right;
};

Node* createNode(int data) {
    Node* newNode = new Node();
    if (newNode != nullptr) {
        newNode->data = data;
        newNode->left = newNode->right = nullptr;
    }
    return newNode;
}

Node* insertNode(Node* root, int data) {
    if (root == nullptr) {
        root = createNode(data);
        return root;
    }

    if (data < root->data) {
        root->left = insertNode(root->left, data);
    } else if (data > root->data) {
        root->right = insertNode(root->right, data);
    }

    return root;
}

void inOrderTraversal(Node* root) {
    if (root == nullptr) {
        return;
    }

    inOrderTraversal(root->left);
    std::cout << root->data << " ";
    inOrderTraversal(root->right);
}

int main() {
    Node* root = nullptr; // 创建一个空的根节点

    // 插入节点
    root = insertNode(root, 50);
    root = insertNode(root, 30);
    root = insertNode(root, 20);
    root = insertNode(root, 40);
    root = insertNode(root, 70);
    root = insertNode(root, 60);
    root = insertNode(root, 80);

    // 中序遍历并打印节点值
    std::cout << "中序遍历结果：";
    inOrderTraversal(root);
    std::cout << std::endl;

    return 0;
}