// A Tree node
class Node {
private:
    char ch;
    int freq;
    Node *left, *right;
public:
    Node(char ch, int freq, Node* left, Node* right) : ch(ch), freq(freq), left(left), right(right) {};
    
    const int getFreq() { return this->freq; };
    Node *getLeft() { return this->left; };
    Node *getRight() { return this->right; };
    const bool isLeaf() { return !this->right && !this->left; };
    const char getChar() { return this->ch; };
};

struct NodeComp
{
    bool operator()(Node *l, Node *r)
    {
        // highest priority item has lowest frequency
        return l->getFreq() > r->getFreq();
    }
};