使用霍夫曼代码解析的未解析外部 C++

问：

我正在做一个涉及霍夫曼树的项目。我已将文件拆分为标题等。

我已经在 HuffmanTree.h 头文件中声明了分配树节点的方法，并在 HuffmanTree.cpp 文件中实现了它。

但是，我仍然收到一个未解决的外部问题。

标题内：

private:

    HuffTreeNode* root;
    int weight = -1;                                                                        // in-class initialization of the data members

    friend ostream& operator<<(ostream& out, const HuffmanTree& tree);
    friend class Comparator;

    bool onlyLeaf(HuffTreeNode* root);
    void encode(HuffTreeNode* root, string str, unordered_map<char, string>& huffMap);
    void decode(HuffTreeNode* root, int& i, std::string str);
    
    
    HuffTreeNode* allocateNode(char letter, int charFreq, HuffTreeNode* left, HuffTreeNode* right);

在.cpp中：

// Allocating the new node to the Huffman Tree
HuffTreeNode* HuffmanTree::allocateNode(char letter, int charFreq, HuffTreeNode* left, HuffTreeNode* right)
{

    HuffTreeNode* node = new HuffTreeNode();

    node->myChar = letter;

    node->myFrequency = charFreq;

    node->myLeft = left;

    node->myRight = right;

    return node;

}

错误：

Severity    Code    Description Project File    Line    Suppression State
Error   LNK2019 unresolved external symbol "public: __thiscall HuffTreeNode::HuffTreeNode(void)" (??0HuffTreeNode@@QAE@XZ) referenced in function "private: class HuffTreeNode * __thiscall HuffmanTree::allocateNode(char,int,class HuffTreeNode *,class HuffTreeNode *)" (?allocateNode@HuffmanTree@@AAEPAVHuffTreeNode@@DHPAV2@0@Z)  CA2 C:\Users\me\source\repos\proj\HuffmanTree.obj   1   

任何帮助将不胜感激。