其實這個還是有點問題的，在偶見情況下會打印出0*x，目前無解唔。。。

原理就是借用線性表，然後做運算直接先插入到後面。

然後遍歷一下，只要指數相同就合併在前面一個裡面，後面的歸0（不刪除）。

列印的時候加一個判斷是否為0的條件就行了。

下面是原始碼：

#include<iostream>
#include<cstring>
using namespace std;
struct Node
{
    double coe;//係數
    int index;//指數
    Node *link;
};
class polynomial
{
private:
    Node 
 
*head, *tail;        //定義頭指標，尾指標
public:
    polynomial();//無參建構函式
    polynomial(double a[], int n[], int number);    //有參建構函式
    ~polynomial();            //解構函式
    void setup();            //求值函式
    void add(double a[], int n[], int number);
    void subtract(double a[], int n[], int number);
    void print();
};
polynomial::polynomial()
{
    head 
 
= NULL;
    tail = NULL;
}
polynomial::polynomial(double a[], int n[], int number)
{
    head = new Node;
    head->index = 0;
    head->coe = 0;
    tail = head;
    for (int i = 0; i < number; i++)
    {
        Node *p = new Node;
        p->coe = a[i];            //儲存係數
        p->index = n[i];        //
 
儲存指數
        p->link = NULL;
        tail->link = p;
        tail = p;
    }
    setup();
}
polynomial::~polynomial()
{

    if (head != NULL)
    {
        head = tail = NULL;
    }
}
void polynomial::add(double a[], int n[], int number)
{
    for (int i = 0; i < number; i++)
    {
        Node *add = new Node;
        add->coe = a[i];
        add->index = n[i];
        tail->link = add;
        tail = add;
    }
    tail->link = NULL;
    setup();
}
void polynomial::subtract(double a[], int n[], int number)
{
    for (int i = 0; i < number; i++)
    {
        Node *add = new Node;
        add->coe = -a[i];
        add->index = n[i];
        tail->link = add;
        tail = add;
    }
    tail->link = NULL;
    setup();
}
void polynomial::setup()
{
    Node *m = head->link;
    Node *p;
    while (m != NULL)
    {
        p = m->link;
        while (p != NULL)
        {
            if (m->index == p->index)
            {
                m->coe = m->coe + p->coe;
                p->coe = 0;
            }
            p = p->link;
        }
        m = m->link;
    }
    tail->link = NULL;
}
void polynomial::print()
{
    if (head == NULL)
    {
        cout << "錯誤，無資料！" << endl;
        exit(1);
    }
    Node *p = head;
    while (p != NULL)
    {
        p = p->link;
        if (p == NULL)
        {
            cout << endl;
            break;
        }
        if (p->coe == 0)
        {
            continue;
        }
        else
        {
            cout << p->coe << "x^" << p->index;
            if (p->link!= NULL&&p->link->coe>0)
            {
                cout << "+";
            }
            
        }
        
        
    }
}
int main()
{
    int number;
    int *index;
    double *coe;
    cout << "歡迎使用多項式計算器，請輸入多項式的元素個數：" << endl;
    cin >> number;
    index = new int[number];
    coe = new double[number];
    for (int i = 0; i < number; i++)
    {
        cout << "請輸入第" << i + 1 << "個多項式的係數: ";
        cin >>coe[i];
        cout << "請輸入第" << i + 1 << "個多項式的指數: ";
        cin >> index[i];
    }
    polynomial test1(coe, index, number);
    test1.print();
    cout << "請輸入相加的多項式的元素個數：" << endl;
    cin >> number;
    delete []index;
    delete []coe;
    index = new int[number];
    coe = new double[number];
    for (int i = 0; i < number; i++)
    {
        cout << "請輸入第" << i + 1 << "個多項式的係數: ";
        cin >> coe[i];
        cout << "請輸入第" << i + 1 << "個多項式的指數: ";
        cin >> index[i];
    }
    test1.add(coe, index, number);
    cout << "相加成功！" << endl;
    test1.print();
    cout << "請輸入相減的多項式的元素個數：" << endl;
    cin >> number;
    delete[]index;
    delete[]coe;
    index = new int[number];
    coe = new double[number];
    for (int i = 0; i < number; i++)
    {
        cout << "請輸入第" << i + 1 << "個多項式的係數: ";
        cin >> coe[i];
        cout << "請輸入第" << i + 1 << "個多項式的指數: ";
        cin >> index[i];
    }
    test1.subtract(coe, index, number);
    cout << "相減成功！" << endl;
    test1.print();

    system("pause");
    return 0;
}