Binary tree. I have code, need little help

#include <iostream>
using namespace std;

struct elem {
	int key;
	elem *left;
	elem *right;
} *root = NULL;

void preorder(elem *t) 
{
	if (t)

	{
		cout << t->key << "\t";
		preorder(t->left);
		preorder(t->right);
	}

}

void inorder(elem *t) 
{
	if (t)
	{
		inorder(t->left);
		cout << t->key << "\t";
		inorder(t->right);
	}
}

void add(int n, elem *&t)
{
	if (t == NULL)
	{
		t = new elem; t->key = n;
		t->left = NULL; t->right = NULL;
	}
	else
	{
		if (t->key>n)
			add(n, t->left);
		else if (t->key<n)
			add(n, t->right);
	}
}

void postorder(elem *t) 
{
	if (t)
	{
		postorder(t->left);
		postorder(t->right);
		cout << t->key << "\t";
	}
}


int height(elem * t)
{
	if (t == NULL)
		return -1;
	int u = height(t->left);
	int v = height(t->right);
	if (u > v)
		return u + 1;
	return v + 1;
}


void printnode(int n, int h)
{
	for (int i = 0; i<h; i++)
		cout << "\t";
	cout << n << endl;
}


void show(elem *t, int h)
{
	if (t == NULL)
		return;
	show(t->right, h + 1);
	printnode(t->key, h);
	show(t->left, h + 1);
}


int count(elem *t)
{
	if (t == NULL) return 0;  return count(t->left) + count(t->right) + 1;
}

 
int count1(elem *t)
{
	if (t == NULL) return 0;
	return count1(t->left) + count1(t->right) + (t->left == NULL) ^ (t->right == NULL);
}

void main()
{
	int a;
	cout << "\n Add elements" << endl;

	do
	{
		cin >> a;
		if (a>0)
			add(a, root);
	} while (a>0);

	int r = count(root);
	cout << "Number of knots " << r << endl;
	int r1 = count1(root);
	cout << "Number of knots with one child" << r1;
	cout << endl;
	cout << endl;
	show(root, 0);
	system("pause");
}