链表，多项式求和

#include <iostream>
using namespace std;
class Poly;
class node
{
    private:
     int coef;//系数
     int exp;//指数
     node *next;
     friend Poly;
     friend void  calculate(Poly &x,Poly &y);
};
class Poly
{
   private:
    node* head;
   public:
    void creat();
    void print();
    void Delete();
    node* Returnhead();
    void print2();
};
void Poly::creat()
{
    node *tail,*p;
    int a,b;
    cout<<"请输入多项式"<<endl;
    p=new node;
    p->exp=0;
    p->coef=0;
    p->next=NULL;
    head=tail=p;
    while(cin>>a>>b&&b>0)
    {
        p=new node;
        p->coef=a;
        p->exp=b;
        p->next=NULL;
        tail->next=p;
        tail=p;
    }
}
node* Poly::Returnhead()
{
    if (head->next)
    return head;
    else
    return NULL;

}
void calculate(Poly &x,Poly &y)
{
    node *p1,*p,*q,*temp;
    p1=x.Returnhead();
    p=p1->next;
    q=y.Returnhead()->next;
   while(q&&p)
   {
     if (p->exp==q->exp)
     {
         p->coef+=q->coef;
          if (p->coef==0)
         {
           p1->next=p->next;
           delete(p);
           p=p1->next;
         }
        else
         {
            p1=p;
            p=p->next;
         }
        q=q->next;//不管怎么样，q1都要向后移
     }
     else
      if (p->exp<q->exp)
     {
         temp=new node;
         temp->coef=q->coef;
         temp->exp=q->exp;
         p1->next=temp;
         temp->next=p;
         q=q->next;
      }
      else
      {
          p1=p;
          p=p->next;
      }
   }
   while(q)
   {
       node*temp;
       temp=new node;
       temp=q;
       p1->next=temp;
       p1=temp;
       q=q->next;
   }
}
void Poly::print()
{
    node*p;
    p=head->next;
   if (p->coef==1)
        cout<<"x"<<'^'<<p->exp;
    else
        if (p->coef==-1)
        cout<<"-x"<<'^'<<p->exp;
        else
         if (p->coef==0)
          p=p->next;
          else
            cout<<p->coef<<'x'<<'^'<<p->exp;
            p=p->next;
    while(p)
    {
       if (p->coef==1)
        cout<<'+'<<'x'<<'^'<<p->exp;
      else
        if (p->coef==-1)
        cout<<"-x"<<'^'<<p->exp;
        else
         if (p->coef==0)
          p=p->next;
          else
            if (p->coef>0)
            cout<<'+'<<p->coef<<'x'<<'^'<<p->exp;
          else
            cout<<p->coef<<'^'<<p->exp;
            p=p->next;
    }
}
void Poly::print2()
{   node *p;
     p=head->next;
     while(p)
    {
       if (p->coef==1)
        cout<<'+'<<'x'<<'^'<<p->exp;
      else
        if (p->coef==-1)
        cout<<"-x"<<'^'<<p->exp;
        else
         if (p->coef==0)
          p=p->next;
          else
            if (p->coef>0)
            cout<<'+'<<p->coef<<'x'<<'^'<<p->exp;
          else
            cout<<p->coef<<'^'<<p->exp;
            p=p->next;
    }
}
void Poly::Delete()
{

    node *p=head,*q;
    while(p)
    {
      q=p->next;
      delete(p);
      p=q;
    }
    cout<<"内存已释放成功"<<endl;
}
int main()
{

    Poly A,B;
    A.creat();
    cout<<"A的表达式为:";
    A.print();
    cout<<endl;
    B.creat();
    cout<<"B的表达式为:";
    B.print();
    cout<<endl;
    cout<<"计算的多项式结果为:"<<endl;
    A.print();
    B.print2();
    cout<<"=";
    calculate(A,B);
   if (A.Returnhead()==NULL)
        cout<<0<<endl;
    else
    A.print();
    cout<<endl;
    A.Delete();
    return 0;
}