Simple Trees

#include <iostream>
#include <vector>

class Node{
private:
    std::string value;
    Node * left, * right;

public:
    Node(std::string value, Node * left = 0, Node * right = 0) :
        value(value), left(left), right(right)
    {};

    operator const char *() const{
        std::vector<const Node *> list(1, this);
        std::string output;
        while(!list.empty()){
            std::vector<const Node *> next;
            for (unsigned int i=0; i < list.size(); i++){
                output += list[i]->value + " ";
                if (list[i]->left)
                    next.push_back(list[i]->left);
                if (list[i]->right)
                    next.push_back(list[i]->right);
            }
            output += "\n";
            list.assign(next.begin(), next.end());
        }
        return output.c_str();
    };
};

int main(){
    std::cout << * new Node("R",
        new Node("A",
            new Node("C",
                new Node("G"),
                new Node("H")
            ),
            new Node("D",
                new Node("I"),
                new Node("J")
            )
        ), new Node("B",
            new Node("E",
                new Node("K"),
                new Node("L")
            ),
            new Node("F",
                new Node("M"),
                new Node("N")
            )
        )
    );
}