Question

I am working on a Binary Tree program for school and I have everything working perfectly. All I am working on now is the proper output. My teacher wants the output to be all the numbers in sorted order with commas after them.

My code that I have sorts the numbers perfectly and prints them, I am just not sure how to remove the comma after the last number.

Current Output: 1, 2, 3, 4,

Needs to be: 1, 2, 3, 4

Here is my code:

void BinaryTree::inorder(tree_node* p)
{
    if(p != NULL)
    {
        if(p->left) 
            inorder(p->left);

        cout << p->data << ", ";

        if(p->right)
            inorder(p->right);
    }
    else
        return;
}

I have tried a few things to make it right but I just can’t figure it out.

Any help would be great.

Thanks.

Answer 1

One easy way is to print the separator character before the data, like this

cout << ", " << p->data;

This way we have changed your problem into skip printing the first comma. This is much easier. Hint: In order to keep track of whether to skip the comma you might need to introduce another argument to the function, since it is a recursive function.

As xmoex points out there is a more elegant way to print this tree resulting in very readable and logic code. Try to find this way for an extra challenge.

An unrelated hint: You can drop the return statement since its redundant – The function will return anyway! Like this:

void BinaryTree::inorder(tree_node* p)
{
  if (p != NULL)
  {
    // stuff goes inside here!
  }
  // no return here - the function will return anyway
}

This will yield less uneccessary code and will help you read your own code if you need to, for example, debug it quickly before a assignment due date.