Question

I was trying to implement a small sample of a linked-list data type. I created a struct Node which holds a value, a struct List which keeps track of all nodes (in linked list format). Finally a class which is a general datatype of both structs.

When I ran the program, I always got a segment fault error as soon as I reached the step:
item->link[i++] = new Node(input)

Code:

struct Node
{
    int val;

    Node();
    Node(int x);
};

struct List
{
    Node *link[20];

    List();
};

class pol
{
    public:
        void read_txt(ifstream &file);

    private:
        List *item;
};

void pol::read_txt(ifstream &file)
{
    int input, i;
    i = 0;

    file >> input;

    cout << "Value read from the file: " << input << endl;

    while(input != 0)
    {
        item.link[i++] = new Node(input);
        file >> input;
        cout << "Value read from the file: " << input << endl;
    }
}

What I am trying to do is, create a new Node with the value of “input” which I get from reading a file. Next, I wanted to create a linked list with all the nodes connected.

Answer 1

The member item is never initialised. As far as I can see there’s no reason at all to make it a pointer. Just make it List item;.