Binary Search Trees (and eventually, a non-binary tree)

Hello world! I am planning on updating my program that renames files named like : homework+essay.docx to homework essay.docx. (My code already works if the file is directly in Downloads, Desktop, or Documents folders.) In order for this program to be of full use, it needs to search the subdirectories. To do that, I am going to have to make a (non-binary) tree. To do that, I need to understand implementation of trees in general, so I am having myself make, and print, a binary search tree; I have not taken a course in data structures. I have my tree made, but I cannot seem to print any of it. Here is my full code:

#include <iostream>
#include <typeinfo>
#include <math.h>

using namespace std;

struct node
{
    int element;
    node * leftnode;
    node * rightnode;
};   //end struct

void createtree(int n, node * a, int max)
{
    if (n < max)
    {
        if (n == 0)
        {
            a->element = pow(2,max-1);
            //cout << "parent node's element == "<<a->element<<endl;
            createtree(1,a,max);
        }   //end if
        else
        {
            a->leftnode = new(nothrow) node;
            a->rightnode = new(nothrow) node;
            node * l = a->leftnode;
            node * r = a->rightnode;
            l->element = a->element-pow(2,max-(n+1));
            r->element = a->element+pow(2,max-(n+1));
            //cout << "the element for the leftnode of level "<<n<<" is "<<l->element<<endl;
            //cout << "the element for the rightnode of level "<<n<<" is "<<r->element<<endl;
            if (n < max-1)
            {
                createtree(n+1,l,max);
                createtree(n+1,r,max);
            }   //end inner if
        }   //end else
    }   //end if
}   //end createtree

void inorder(node * a)
{
    //Remember, this should print the first child, then the parent, and then the other child.
    //To do this, it must go to the lowest level first.
    //After that, access the parent node
    //Finally, go to the childnode.

    //First, make the necessary declarations...
    node * templeft = a->leftnode;
    node * tempright = a->rightnode;
    //if the pointer is not null
    if (a != 0)
    {
        inorder(templeft);
        //inorder(a->leftnode);
        cout << a->element << endl;
        //inorder(a->rightnode);
        inorder(tempright);
    }   //end if
}   //end inorder

int main()
{
    int x;
    cout << "Enter the number of levels of nodes (include parent node): ";
    cin >> x;
    node * t;
    t = new(nothrow)node;
    createtree(0,t,x);
    inorder(t);
    //This is test code; I did this to test my idea out before the implementation took place.
    node b;
    b.element = 32;
    b.leftnode = new(nothrow) node;
    b.rightnode = new(nothrow) node;
    node * l = b.leftnode;
    node * r = b.rightnode;
    l->element = 16;
    r->element = 48;
    cout << "l->element == " << l->element << endl;
    cout << "r->element == " << r->element << endl;
    return 0;
}

(Sorry for all the comments.)
It is throwing a segmentation fault on the

node * templeft = a->leftnode;

statement. Even if I forgo the use of temporary pointers (and just use a->leftnode, a->rightnode directly), it throws a segmentation fault on the

inorder(a->leftnode);

statement. I have no idea why this is; I would think that it would be because the compiler doesn't know what a->leftnode, a->rightnode are, but I might be wrong. Remember that inorder(tree * a) is supposed to be PRINTING THE BINARY TREE via in-order traversal. I couldn't just use leftnode,rightnode = new(nothrow)node tree. I am out of ideas; can anyone help?