Change this:
if(data<=node->data)
{
insert(node->left, data);
return(node);
}
else
{
insert(node->right, data);
return(node);
}
to:
if(data<=node->data)
{
node->left = insert(node->left, data);
}
else
{
node->right = insert(node->right, data);
}
return (node);
also the code in your main should be:
root = insert(root, 5);
root = insert(root, 3);
root = insert(root, 6);