public: virtual ~Node() = 0;

public: std::uint32_t symbol;

public: explicit Leaf(std::uint32_t sym);

public: std::unique_ptr<Node> leftChild; // Not null

public: std::unique_ptr<Node> rightChild; // Not null

public: explicit InternalNode(std::unique_ptr<Node> &&left, std::unique_ptr<Node> &&right);

/*---- Fields ----*/

public: InternalNode root;

// Stores the code for each symbol, or null if the symbol has no code.

// For example, if symbol 5 has code 10011, then codes.get(5) is the list [1,0,0,1,1].

private: std::vector<std::vector<char> > codes;

/*---- Constructor ----*/

// Constructs a code tree from the given tree of nodes and given symbol limit.

// Each symbol in the tree must have value strictly less than the symbol limit.

public: explicit CodeTree(InternalNode &&rt, std::uint32_t symbolLimit);

/*---- Methods ----*/

// Recursive helper function for the constructor

private: void buildCodeList(const Node *node, std::vector<char> &prefix);

// Returns the Huffman code for the given symbol, which is a list of 0s and 1s.

public: const std::vector<char> &getCode(std::uint32_t symbol) const;