Singly linked list application --- one-ary polynomial

[Description of Problem] Write a program to store polynomials with a singly linked list and implement the function of adding two unary polynomials A and B. A and B are initially in ascending order, and the sum of A and B is in descending order. For example:
Polynomial A: 1.2X ^ 0 2.5X ^ 1 3.2X ^ 3 -2.5X ^ 5
Polynomial B: -1.2X ^ 0 2.5X ^ 1 3.2X ^ 3 2.5X ^ 5 5.4X ^ 10
Polynomials A and B Sum: 5.4X ^ 10 6.4X ^ 3 5X ^ 1

【Input form】 Any two polynomials A and B

[Output form] The coefficient and exponent of a term in the polynomial, the coefficient retains one decimal place.

[Sample input] 1.2 0 2.5 1 3.2 3 －2.5 5
－1.2 0 2.5 1 3.2 3 2.5 5 5.4 10
2

[Sample output] 6.4 3

[Sample description] The first polynomial coefficient and exponent pair are separated by a space. The
second polynomial coefficient and exponent pair are separated by a space and
the second term coefficient and exponent are output. The coefficient and exponent are separated by a space , The coefficient retains a decimal

[Scoring criteria] must be implemented with a linked list.

#include <iostream>
#include <cstdio>
using namespace std;
struct Node
{
    float coef;
    int exp;
    Node *next;
};
class Polynomial
{
public:
    Polynomial();
    Polynomial(const Polynomial &B);
    Polynomial operator+ (Polynomial &B);
    void Printk(int k);
    void Print();
private:
    Node *first;
};
Polynomial :: Polynomial()
{
    Node* r =NULL, * s=NULL;
    first = new Node;
    r=first;
    char c;
    do
    {
        s=new Node;
        scanf("%f%d", &s->coef, &s->exp);
        r->next=s;
        r=s;
        c=getchar();

    }while(c != EOF&& c != '\n');
    r->next=NULL;
}
Polynomial::Polynomial(const Polynomial &B)
{
    first=B.first;
}
Polynomial Polynomial:: operator+(Polynomial &B)
{
    Node *pre =first,*p=pre->next;
    Node *qre=B.first,*q=qre->next;
    while(p && q)
    {
        if(p->exp < q->exp)
        {
            pre=p;
            p=p->next;
        }
        else if(p->exp > q->exp)
        {
            qre->next=q->next;
            q->next=p;
            pre->next=q;
            pre=q;
            q=qre->next;

        }
        else
        {
            p->coef = q->coef+p->coef;
            if(p->coef==0)
            {
                pre->next = p->next;
                delete p;
                p=pre->next;
            }
            else
            {
                pre=p;
                p=p->next;
            }
            qre->next=q->next;
            delete q;
            q=qre->next;
        }
    }
    if(q) pre->next = q;
    return *this;
}
void Polynomial::Print()
{
    Node *p=first->next;
    if(p)
        cout<<p->coef<<"x"<<p->exp;
    p=p->next;
    while(p)
    {
        if(p->coef>0)
            cout<<"+"<<p->coef<<"x"<<p->exp;
        else
            cout<<p->coef<<"x"<<p->exp;
        p=p->next;
    }
}
void Polynomial::Printk(int k)
{
    Node* p=first;
    int cnt = 0;
    while (p&&cnt < k)
    {
        p= p->next;
        cnt++;
    }
    Node* prek=first;
    while(p)
    {
        p=p->next;
        prek = prek->next;
    }
    printf("%.1f %d",prek->coef,prek->exp);
}
int main()
{
    Polynomial A,B;

    //A.Print();B.Print();
    A = A+B;
    //cout<<"½á¹ûÊÇ:";
    //A.Print();
    int k;
    cin>>k;
    A.Printk(k);
    return 0;


}