Storing values in a struct in a linked list - c++

Question

I'm wondering how I would go about storing a value into a struct that is part of a linked list of structs. I have:
struct polynomial
{
polynomial(string newCoefficient, string newPower, polynomial *nextPtr);
string coefficient;
string power;
polynomial *next;
};
class linkedList
{
public:
void createList();
private:
polynomial *head;
};
For this assignment, we need to do some parsing when gathering input values. For example, we are to input two numbers separated by a space (ex. 7 9 or 10 8). Therefore, in void createList(), I want to read in a line using string, convert it to a char array to strip down the values, then store that value into polynomial.coefficient and polynomial.power, for each node in the linked list.
Or, I was searching some information up, and I was thinking maybe I can input two int values and then use stringstream to convert them into strings and them store into coefficient and power.
Either way, can you help introduce me to the concept of storing a value into a linked listed struct?
EDIT: I have added the overloaded constructor:
polynomial:: polynomial ( string newCoefficient, string newPower, polynomial *nextPtr )
{
coefficient = newCoefficient;
power = newPower;
next = nextPtr;
};

Answer 1

You are mixing C-style practice with C++ practice.
In C++, you generally separate the data from the container. Look at how std::list works.
Even if you don't want to get into templating, you can still do this:
struct polynomial {
string coefficient;
string power;
};
struct listnode {
polynomial data;
listnode *next;
};
If you really want to have the head concept, you can either keep a 'dummy head' where you store one listnode that has nothing in it.
Alternatively, if you really want the next pointer in polynomial and you want a way to copy over an existing element without nuking the pointer, just make a setter function:
void polynomial::set( const string& inCoeff, const string & inPower );

Answer 2

I tested the following code which may help you out:
struct Polynomial {
string coefficient;
string power;
Polynomial* next;
Polynomial(const string& coeff, const string& pow) : coefficient(coeff), power(pow), next(NULL) {}
};
// linked-list of Polynomials
struct LinkedList {
Polynomial* head;
LinkedList() : head(NULL) {}
// add to end of list
void add(const string& coeff, const string& pow) {
if(head == NULL)
head = new Polynomial(coeff, pow);
else {
Polynomial* n;
for(n = head; n->next != NULL; n = n->next);
n->next = new Polynomial(coeff, pow);
}
}
// check if results are correct
void print() {
for(Polynomial* n = head; n != NULL; n = n->next)
cout << n->coefficient << " " << n->power << endl;
}
};
// somewhere in main()
LinkedList ll;
...
// read input values
ll.add(coeff1, pow1);
ll.add(coeff2, pow2);
ll.add(coeff3, pow3);
// check results
ll.print();
Note your Polynomial struct members need not be strings. Instead you could just parse your input and store cofficient as float and power as int (All polynomial exponents are integers).