public static void preOrder(Node root) {
        if(root == null){
            return;
        }
        System.out.print(root.data+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

if(!root) return;
    process.stdout.write(`${root.data} `);
    if(root.left) preOrder(root.left);
    if(root.right) preOrder(root.right);

void preOrder( struct node *root) {
    if (root != NULL) {
        printf("%d ", root->data);
        preOrder(root->left);
        preOrder(root->right);
    }
}