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Problem with array of pointers

  1. Apr 25, 2008 #1
    There was a problem in an assignment I was solving, which asked me to break up the elements of a linked list into 3 different linked lists. Rather than creating 3 linked lists, I tried to create a general program for any such number and hence used an array of pointers.

    A node in my linked list is given as such:

    Code (Text):

    struct node {
        int data;
        node* next;
    };
     
    and i had a function to add elements to it:

    Code (Text):

    node* getNewNode(int data) {
        node* x = new node;
        if(x == NULL) {
            cout<<"Error: OVERFLOW";
            exit(0);
        }

        x->data = data;
        x->next = NULL;
        return x;
    }
       
    void addElement(node** start, int data) {
        node* x = getNewNode(data);
        if(*start == NULL) {
            *start = x;
        } else {
            x->next = *start;
            *start = x;
        }
    }
     
    and a function to display the list:

    Code (Text):

    void displayList(node* start) {
        node* x = start;
       
        while(x != NULL) {
            cout<<x->info;
            x = x->next;

            if(x != NULL) {
                cout<<";";
            }
         }
    }
     
    and all of this works perfectly fine if i use something like this:

    Code (Text):

    node* y;
    addElement(&y, 21);
    addElement(&y, 13);
    displayList(y);
     
    But, if i try using an array of pointers, for example:

    Code (Text):

    node** iList = new node*[2];
    node* m = *(iList+0);
    addElement(&m, 21);
    addElement(&m, 11);
    displayList(m);
     
    The output is something like:

    Code (Text):

    21;11;<random-number>
     
    and then the program segfaults. What am I doing wrong here? For all I know, *(iList+0) is a variable of type node* and hence should satisfy the requirements for it to be the first element in a linked list.. why is it not working?
     
  2. jcsd
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