Question

template<typename T>
void traverse_binary_tree(BinaryTreeNode<T>* root,int order = 0)// 0:pre, 1:in , 2:post
{
    if( root == NULL ) return;

    if(order == 0) cout << root->data << " ";

    traverse_binary_tree(root->left,order);

    if(order == 1) cout << root->data << " ";

    traverse_binary_tree(root->right,order);

    if(order == 2) cout << root->data << " ";

}

Is there a better way to write this function?

Answer 1

No.

Kidding. I think it looks pretty efficient.

I would enum the order values, for readability.

...
enum TOrder {ORDER_PRE, ORDER_IN, ORDER_POST};

template<typename T>
void traverse_binary_tree(BinaryTreeNode<T>* root,TOrder order = ORDER_PRE) {
...