c++ - 类的析构函数中的访问冲突读取位置

Question

我已经构建了 Graph 类、一个构造函数和一个析构函数。我的问题是:当我编译这段代码时，我在 delete [] mat[i]; 这行出错，错误是“访问冲突读取位置 0xDDDDDDCD”。而且我不确定我做错了什么。我的意思是我只删除动态分配的内存。稍后编辑:即使我使用这个而不是我的方法:

Graph(int nr_noduri) {


this->nr_noduri = nr_noduri;
    mat = new bool* [nr_noduri];
    for (int i = 0; i < nr_noduri; i++) {
        mat[i] = new bool[nr_noduri];
    }
    for (int i = 0; i < nr_noduri; i++) {
        for (int j = 0; j < nr_noduri; j++) {
            mat[i][j] = 0;
        }
    }
}

我的代码是:

 #include <iostream>
#include <cstdlib>
using namespace std;

class Graph {
    bool** mat;
    int nr_noduri;

public:
    Graph(int nr_noduri) {
        this->nr_noduri = nr_noduri;
        mat = (bool**)calloc(nr_noduri, sizeof(bool*));
        for (int i = 0; i < nr_noduri; i++) {
            mat[i] = (bool*)calloc(nr_noduri, sizeof(bool));
        }
    }

    int size() {
        return nr_noduri;
    }

    void addArc(int v, int w) {
        if (v < nr_noduri && w < nr_noduri) {
            mat[v][w] = true;
        }
        else cout << "Not enough nodes !" << endl;
    }

    bool isArc(int v, int w) {
        return (mat[v][w] == true);

    }

    void print() {
        for (int i = 0; i < nr_noduri; i++) {
            cout << endl;
            for (int j = 0; j < nr_noduri; j++) {
                cout << mat[i][j] << " ";
            }
        }
        cout << endl;
    }

    ~Graph() {
        //cout << nr_noduri;
        for (int i = 0; i < nr_noduri; i++) {
            delete [] mat[i];
        }
        delete[] mat;
    }

    friend void dfs(Graph g, int v, bool vazut[]);
};

void dfs(Graph g, int v, bool vazut[]) {
    int w;
    vazut[v] = true;
    for (w = 0; w < g.size(); w++) {
        if (g.isArc(v, w) && !vazut[w]) {
            cout << v << "->" << w;
            dfs(g, w, vazut);
        }
    }
}


int main() {
    int nr_noduri;
    cin >> nr_noduri;
    Graph v(nr_noduri);
    v.print();
    v.addArc(1, 2);
    v.addArc(2, 5);
    cout << v.isArc(1, 2) << endl;
    v.print();
    bool vazut[100];
    dfs(v, 1, vazut);
    return 0;
}

Answer 1

您不能使用 delete释放由 calloc 分配的内存(或任何 malloc 函数族)。使用 new而不是分配内存。

Graph(int nr_noduri) {
    this->nr_noduri = nr_noduri;
    mat = new bool*[nr_noduri];
    for (int i = 0; i < nr_noduri; i++) {
        mat[i] = new bool[nr_noduri];
    }
}

更好的是，使用 std::vector<std::vector<bool>>保存数据。

class Graph {
   std::vector<std::vector<bool>> mat;

   Graph(int nr_noduri) : mat(nr_noduri, std::vector<bool>(nr_noduri) {}

   ...
};