怎么实现不按指数递增输入也能实现多项式相加

//一元多项式求和头文件
#include<iostream>
using namespace std;
template<class DataType>
//定义单链表结点
struct Node
{
    DataType coef, exp;
    Node<DataType> *next;
};
//定义存放一元多项式的类
template<class DataType>
class Linklist
{
private:
    Node<DataType> *first;
    int size;
public:
    Linklist();
    void Init();
    void Print();
    //void creatDuoX(DataType &Px,int n);
    Linklist<DataType> operator+(Linklist &p2);
};

template<class DataType>
Linklist<DataType>::Linklist()
{
    first = new Node<DataType>;
    first = NULL;
    size = 0;
}



//实现一元多项式单链表的初始化
template<class DataType>
void Linklist<DataType>::Init()
{
    cout << "多项式的元素个数为:";
    cin >> size;
    DataType x, y;
    cout << "请输入第1项的系数:";
    cin >> x;
    cout << "请输入第1项的指数:";
    cin >> y;
    Node<DataType> *m;
    m = new Node<DataType>;
    m->coef = x;
    m->exp = y;
    m->next = NULL;
    first = m;
    for (int i = 2; i <= size; i++)
    {
        cout << "请输入第" << i << "项的系数:";
        cin >> x;
        cout << "请输入第" << i << "项的指数:";
        cin >> y;
        Node<DataType> *n;
        n = new Node<DataType>;
        n->coef = x;
        n->exp = y;
        n->next = NULL;
        m->next = n;
        m = n;
        }
}



//实现一元多项式单链表实的输出
template<class DataType>
void Linklist<DataType>::Print()
{
    Node<DataType> *m = first;
    while (m != NULL)
        {
            if (m == first)
            {
                if (m->coef != 0 && m->exp != 0)
                {
                    cout << m->coef << "x^" << m->exp;
                }
                else if (m->coef != 0 && m->exp == 0)
                {
                        cout << m->coef;
                }
            }
            else
            {
                if (m->coef > 0 && m->exp != 0)
                {
                    cout << "+" << m->coef << "x^" << m->exp;
               }
               else if (m->coef<0 && m->exp != 0)
               {
                    cout<< m->coef << "x^" << m->exp;
               }
               else if (m->coef>0 && m->exp == 0)
               {
                    cout << "+" << m->coef;
               }
               else if (m->coef < 0 && m->exp == 0)
               {
                    cout << m->coef;
               }
            }
            m = m->next;
        }
        cout << endl;
}



//实现一元多项式单链表的相加
template<class DataType>
Linklist<DataType> Linklist<DataType>::operator+(Linklist &p2)
{
    //声明工作指针
    Node<DataType> *pre, *p, *qre, *q;
    //初始化工作指针
    pre = this->first;
    p = pre->next;
    qre = p2.first;
    q = qre->next;
    while (p != NULL&&q != NULL)
    {
        //p->exp < q->exp：指针 p 后移
        if (p->exp < q->exp)
        {
            pre = p;
            p = p->next;
        }
        //p->exp > q->exp：将结点 q 插到结点 p 之前，指针 p 指向他原指结点的下一个结点
        if (p->exp > q->exp)
        {
            Node<DataType> *s;
            s = q->next;
            pre->next = q;
            q->next = p;
            q = s;
        }
        //p->exp == q->exp：
        if (p->exp == q->exp)
        {
            //p->coef = p->coef + q->coef
            p->coef = p->coef + q->coef;
            if (p->coef == 0)
            {
                //使指针 p 指向它原指结点的下一个结点
                pre->next = p->next;
            //删除结点 p
                delete p;
                p = p->next;
            }
            else
            {
                pre = p;
                p = pre->next;
            }
            //使指针 q 指向它原指结点的下一个结点
            qre->next = q->next;
            //删除结点 q
            delete q;
            q = qre->next;
        }
    }
    //如果 q 不为空，将结点 q 链接在第一个单链表的后面。
    if (q != NULL)
    {
        pre->next = q;
        delete p2.first;
    }
    return *this;
}
#include<iostream>
//引入一元多项式之单链表实现的头文件
#include "ss.h"
using namespace std;
int main()
{
    //声明一元多项式单链表
    Linklist<int> p1, p2, p3;
    //int n;
    cout << "请按指数由小到大的顺序定义多项式A(x):" << endl;
    p1.Init();
//    p1.creatDuoX(p1,n);
    cout << "输入的多项式A(x)为:";
    p1.Print();
    cout << "\n请按指数由小到大的顺序定义多项式B(x):" << endl;
    p2.Init();
//    p2.creatDuoX(p2,n);
    cout << "输入的多项式B(x)为:";
    p2.Print();
    //一元多项式相加
    p3 = p1 + p2;
    cout << "\n多项式A(x)和多项式B(x)的和为:" << endl;
    p3.Print();
    return 0;
}