Question

I am having issue returning a pointer to a struct. Can some explain what I am doing wrong? I want the search() to return a pointer to the matching input. That will be stored into a vector in case their are duplicates in the “array”. This seems to work however I cannot get the “data” from the pointer returned?

struct Node
{
    int data;
    Node *left;
    Node *next;
};

vector<Node *> array;


void find(int & input)
{
     currentSize = 0;
     vector<Node *> hold;

    for( int i = 0; i < array.size( ); i++ ){
        if(search(array[i], input) != NULL)
        {
            hold.push_back(search(array[i], input));
        }
        else{
            cout << "The Key is not found" << endl;
        }

    }

    for(int i = 0; i < hold.size(); i++)
    {
        cout << hold[i] << endl;
        //Problem here:: I want to see the "data" that the search function returned not the hex value
    }
}


Node * search(Node * x, const int & input)
{
    if( x == NULL )
    {
       return NULL;
    }
    else
    {
        if(input == x->element)
        {
            return x;
        }
            search(x->left, input);
            search(x->next, input);
    }
}

Answer 1

You need to turn compiler warnings on.

Not all code paths of search return a value, in particular, is the warning you should be getting if your compiler isn’t being brain dead.

To fix this, replace this:

            search(x->left, input);
            search(x->next, input);
    }
}

with:

            Node* leftSearch = search(x->left, input);
            if (leftSearch)
              return leftSearch;
            return search(x->next, input);
    }
}

The search() recursive calls do not automatically ferry their return values over to the return value of the current function. 🙂

In addition, as noted by Zack, you need to look at some subfield of the Node to print it. First check if the return value is nullptr (or NULL in non-C++11 capable compilers) (if it is null, you can’t dereference it safely, and it indicates the search failed).

If it isn’t nullptr‘, do a ->data on it before you print.

Ie, change:

    cout << hold[i] << endl;

to:

    if (hold[i]) {
      cout << "Found: " << hold[i]->data << "\n";
    } else {
      cout << "Not Found\n";
    }

note that I’m not using std::endl, because I don’t see the need to flush the buffer on each line.