c - C中的强连通分量

Question

我正在使用 Tarjan 算法实现强连接组件。我将输入作为节点和边的链接列表。但是，gcc 编译器每次在递归函数中都会给出分段错误（在 while 循环中，我正在检查顶点的相邻节点）。

知道这段代码有什么问题吗？

void strongconnect(int Vertex)
{
 struct sc_node * Ver;
 Ver = search_node(Vertex);
 Ver->sc_index = ind; //accessing the index information of node
 Ver->sc_lowlink = ind; // accessing the link information of node
 //Ver->visited = 1;
 ind++;
 int w;
 push(Vertex);

 struct sc_node * to_link, *to_link1;
 int to_lowlink,to_index;
 int flowlink;
 int min;
 int from_index;

 edge_trav = edge_head;    

 while(edge_trav != NULL)   //accessing linked list of edges
 {
   if(edge_trav->from_vertex == Vertex)
   {
     to_link = search_node(edge_trav->to_vertex);
     to_lowlink = to_link->sc_lowlink;
     to_index = to_link->sc_index;
     to_link1 = search_node(Vertex);
     flowlink = to_link1->sc_lowlink;
     from_index =  to_link1->sc_index;

     if(to_index == 0)
     {   Vertex = to_link->sc_data;
          printf("INSIDE RECURSION");
          strongconnect(Vertex);   // recursive loop
          min = minimum(flowlink,to_lowlink);
          to_link1->sc_lowlink = min;
     }
     else 
     {
       min =  minimum(flowlink, from_index);
       to_link1->sc_lowlink = min;
     }  }
  edge_trav = edge_trav->next;
  }
  Ver = search_node(Vertex);
  if(Ver->sc_lowlink == Ver->sc_index)
  {
   do
   {
    w = pop();
    printf("%d\t",w);
   }while(w != Vertex);
  }
}

Answer 1

我建议你用 gcc 编译你的程序，-s然后用valgrind. 这是非常有用的内存泄漏检查器。有了它，您可以自己弄清楚您的程序是否访问了非法的内存位置。正如@Dogbert 指出的那样，看起来您正在取消引用一个NULL指针。