Question

I was trying to create a linked list with structs. The idea is to use 2 different stucts, one which is a node, and another which is a pointer to the nodes (so, I can link the nodes together).

But I wanted to initialize the pointer to the first node as NULL, and create subsequent nodes later:

I am having an error in the 2 constructor methods (List and Polynomial), I can’t use the operator = like the way I am. But I can’t understand why.

struct List
{
    //Data members to hold an array of pointers, pointing to a specific node
    Node *list[100];

    //Default constructor
    List();
};

List::List()
{
    *list[0] = NULL;
}

class Polynomial
{
    public:
    [...]

    private:
        List *poly;                         //Store the pointer links in an array
        Node first_node;
        int val;
};

Polynomial::Polynomial()
{
    poly = new List();
}

/*******************************************************************************************************************************/
// Method   : initialize()
// Description  : This function creates the linked nodes
/*******************************************************************************************************************************/
Polynomial::void initialize(ifstream &file)
{
    int y[20];
    double x[20];
    int i = 0, j = 0;

    //Read from the file
    file >> x[j];
    file >> y[j];

    first_node(x[j], y[j++]);                       //Create the first node with coef, and pwr
    *poly->list[i] = &first_node;                       //Link to the fist node

    //Creat a linked list
    while(y[j] != 0)
    {
        file >> x[j];
        file >> y[j];
        *poly->list[++i] = new Node(x[j], y[j++]);
    }

    val = i+1;                              //Keeps track of the number of nodes
}

I have been getting errors in the Polynomial constructor and the List constructor.

Answer 1

It seems not like the link list. Maybe you need a struct node (right ?) contain information and List contain many node after ? If this two, I has two solutions:

first. very (and very) common.

typedef struct nNode{
  int info;
  string name;
  //and any information you want this node has.
  struct nNode *pNext;
} Node;

Second. Style like I see in your code.

typedef struct nNode{
  int info;
  string name;
  //and any information you want this node has
}Node;
typedef struct nList{
  Node node;
  struct nList *pNext;
} List;

You see, the second version looks like the first 🙂