多项式乘法

//数据结构作业

#include<iostream>
using namespace std;
 class SingleList;
 istream &operator>>(istream &in, SingleList &A);
 ostream &operator<<(ostream &out,const SingleList &A);
 class node
 {
private:
     int coef;
     int exp;
     node *next;
     friend class SingleList;
     friend void operator*(const SingleList &A,const SingleList &B);

};
 class SingleList
 {
 private:
     node *head;
 public:
     void creat(istream &in);
     void print(ostream &out);
     friend void operator*(const SingleList &A,const SingleList &B);
     friend istream &operator>>(istream &in, SingleList &A);
     friend ostream &operator<<(ostream &out,const SingleList &A);
     void Delete();
 };
 
void SingleList::creat(istream &in)
 {
     node *tail,*p;
     int a,b;
     head=tail=NULL;
     while(cin>>a>>b&&b>=0)
     {
         p=new node;
         p->coef=a;
         p->exp=b;
         p->next=NULL;
         if (head==NULL)
            head=p;
         else
            tail->next=p;
            tail=p;
     }
        return;
}
istream  &operator>>(istream &in, SingleList &A)
{
    A.creat(in);
    return in;
}
void SingleList::Delete()
{
    node *p,*q;
    p=head;
    while(p)
    {
    q=p;
    p=p->next;
    delete(q);
    }


}
void SingleList::print(ostream &out)
{
    node*p;
    p=head;
    if (p->coef==1)
    {
        if(p->exp==1)
        cout<<"x";
        else
            if (p->exp==0)
            cout<<"1";
        else
            cout<<"x"<<"^"<<p->exp;
    }
    else
    {
        if (p->coef==-1)
        {
            if (p->exp==1)
            cout<<"-x";
            else
                if (p->exp==0)
                cout<<"-1";
            else
                cout<<"-x"<<"^"<<p->coef;
        }
        else
         if  (p->coef!=0)
           if (p->exp==1)
                    cout<<p->coef<<"x";
              else
            if   (p->exp==0)
                   cout<<p->coef;
              else
                   cout<<p->coef<<'x'<<'^'<<p->exp;
    }
          p=p->next;
   while(p)
    {
       if (p->coef==1)
       {
           if (p->exp==1)
            cout<<"+x";
           else
            if (p->exp==0)
            cout<<"+1";
           else
             cout<<"+x"<<p->exp;
       }
      else
        if (p->coef==-1)
        {
            if (p->exp==1)
            cout<<"-x";
            else
                if (p->exp==0)
                cout<<"-1";
            else
            cout<<"-x"<<'^'<<p->exp;
        }
        else
           if (p->coef!=0)
            if (p->coef>0)
            {
                if (p->exp==0)
                    cout<<"+"<<p->coef;
                else
                    if (p->exp==1)
                    cout<<"+"<<p->coef<<"x";
                 else
                    cout<<'+'<<p->coef<<'x'<<'^'<<p->exp;
            }
          else
          {
          if(p->exp==0)
            cout<<p->coef;
          else
            if (p->exp==1)
            cout<<p->coef<<"x";
          else
            cout<<p->coef<<'x'<<'^'<<p->exp;
          }
            p=p->next;

    }
           cout<<endl;

}
ostream &operator<<(ostream &out, SingleList &B)
{
    B.print(out);
    return out;
}
 void operator*(const SingleList &A,const SingleList &B)
{
    node *chead,*a,*b,*p,*q,*temp;//*q为*p的前一个指针
    chead=new node;//先建立一个表头节点
    chead->coef=0;
    chead->exp=-1;
    chead->next=NULL;
    a=A.head;//先从A开始扫描，每遇到一个新节点就将其与B中的每一个节点相乘(结果为temp),乘积结果在C中找出它相应的位置
    while(a)
    {
        b=B.head;
        q=chead;
        while(b)
        {
            temp=new node;
            temp->coef=a->coef*b->coef;
            temp->exp=a->exp+b->exp;
            temp->next=NULL;
            p=chead->next;
            while(p&&p->exp>temp->exp)//如果该节点的指数小于C中的每一个节点的指数，就向后移
            {
                q=p;
                p=p->next;
            }
            if (p==NULL) //如果是空节点，就直接放在最后
            {
                q->next=temp;
            }
            else
            if (p->exp==temp->exp)
            {
             p->coef=p->coef+temp->coef;//系数相加
             if(p->coef==0)//如果相加后系数为0，就将该节点删去.
             {
                 q->next=p->next;
                 delete(p);
             }
            }
            else
            {
                if (p->exp<temp->exp)//如果系数小于temp,就将其插在q与o之间
                {
                    q->next=temp;
                    temp->next=p;
                }
            }
            b=b->next;
        }
        a=a->next;
    }
    p=chead->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<<'x'<<'^'<<p->exp;
            p=p->next;
    }
    cout<<endl;
    p=chead;
    while(p)
    {
     q=p;
     p=p->next;
     delete(q);
    }
}
   int main()
  {
      SingleList A,B;
      cout<<"*************************欢迎来到B14040312的小小多项式乘法计算器***************************"<<endl;
      cout<<"请输入A的表达式"<<endl;
      cin>>A;
      cout<<"A的表达式为:";
      cout<<A;
      cout<<"请输入B的表达式"<<endl;
      cin>>B;
      cout<<"B的表达式为:";
      cout<<B;
      cout<<"计算结果为:";
      A*B;
      A.Delete();
      B.Delete();
      return 0;
  }