Question

我创建了一个程序，到目前为止，它为霍夫曼编码程序创建了节点的二叉树。出于某种原因，当调试器到达测试两个子节点是否等于Null的时候（因此树上有一个实际字符而不仅仅是父节点），程序会冻结。代码是每个对象的代码数组，包括具有两个成员变量的代码结构。

void Huff::traverse(Node* root, vector<Code>* code, string code_base){
    if(root->childL == NULL && root->childR == NULL){ //stops here
        Code c;
        c.content = root->litteral;
        c.symbol = code_base;
        code->push_back(c);
    }else{
        if (root->childL != NULL)
            traverse(root->childL, code, code_base + '0');
        if (root->childR != NULL)
            traverse(root->childR, code, code_base + '1');
    }
}

调用此函数的函数是（它被称为结束）：

vector<Code>* Huff::compress(){
    //-------GETTING WEIGHTS/FREQUENCIES------
    vector<Node *>* nodes = new vector<Node*>; // Vector of nodes for later use
    map<char, int>* freq = new map<char, int>; //  Map to find weight of nodes
    for(unsigned int i = 0; i < content.length(); i++)
        (*freq)[content[i]]++; 
    CopyTo copyto(nodes); //sets vector<Node*> to copy to 
    for_each(freq->begin(), freq->end(), copyto); // Copies 
    delete freq;
    vector<Node *>::iterator beg = nodes->begin();

    //-------SETTING UP TO BUILD TREE------
    if(nodes->size() % 2 == 1){ //makes sure there are an even number of nodes
        Node* fill = new Node;
        fill->set_node(0, '*', NULL, NULL);
        nodes->push_back(fill);
    }
    huff_sort(nodes); // sort nodes by weight

    //-------BUILDING TREE------
    while(nodes->size() != 1){ //Sorts nodes by weight and then removes two of them and replaces them with one
        int w= (**beg).weight + (**(beg+1)).weight;
        Node* p = new Node;
        p->set_node(w, '*', *nodes->begin(), *(nodes->begin()+1)); //making it the parent node of the two lowest nodes
        nodes->erase(nodes->begin(), nodes->begin()+2);
        unsigned int i = 0;
        while(w > (*nodes)[i]->weight && i <= nodes->size()){ //finds where to insert the parent node based on weight
            i++;
        }
        if(i > nodes->size()) //if it needs to be inserted at the end
            nodes->push_back(p);
        else
            nodes->insert(nodes->begin()+i, p);
        delete p;
    }

    //-------TRAVERSING TREE------
    Node* root = (*nodes)[0];
    delete nodes;
    vector<Code>* codes;
    traverse(root, codes , "");
    delete root;
    return codes;
}

注意：遍历树代码块之前的while循环是树的创建位置

Answer 1

检查root是否指向某个内容（if (root) ...）。这应该有所帮助。

Answer 2

致电delete nodes;后，您需要说traverse。您现在拥有的内容会在致电root之前NULL指向traverse。

C ++冻结测试成员变量是否等于NULL

2 个答案: