int main() { //main program
NodePtr root = createExpressionTree();
std::cout << "The Answer is: " << root->Evaluate();
std::cout << "\nIn InOrder ";
root->InOrder();
std::cout << "\nIn PreOrder ";
root->PreOrder();
std::cout << "\nIn PostOrder ";
root->PostOrder();
}
void TreeNode::InOrder() const { //traverses the tree InOrder
if (left) left->InOrder();
std::cout << operation << " ";
if (right) right->InOrder();
}
