#include<iostream.h>
struct Term{
    float coef;//系数
    int exp;//指数
    struct Term *next;
    Term(){};
    Term(float c,int e,Term *p):coef(c),exp(e){next=p;}
    Term*InsertAfter(float c,int e);//返回指针类型函数
};//结点类

Term* Term::InsertAfter(float c,int e)
{  
    next=new Term(c,e,next);//构造新项结点<c,e>,插在当前结点及其后继结点之间
    return next;  //函数返回新结点地址
}

ostream& operator<<(ostream& out, Term&A)
{
    if(A.coef==0)return out;
    switch(A.exp){
    case 0:out<<A.coef;break;
    case 1:if(A.coef!=1)out<<A.coef;
        out<<"X";break;
    default:if(A.coef!=1)out<<A.coef;
            out<<"X^"<<A.exp;break;
    }
    return out;
}
//----------------------------------------------------------------------------------------
class Polynominal
{
public:
    Polynominal();
    ~Polynominal();
    void AddTerms(istream& in);//添加多项式项,即构造一个多项式,按降幂次序输入
    void Output(ostream& out);//输出多项式
    Polynominal& PolyAdd(const Polynominal& x,const Polynominal& y);//加法函数
    Polynominal& PolySub(const Polynominal& x,const Polynominal& y);//减法函数
    Polynominal& PolyMul(const Polynominal& x,const Polynominal& y);//乘法函数
    //void operator=(const Polynominal &x);
    int comp(int x,int y);
    void Clear();
private:
    struct Term *head;
    friend ostream& operator<<(ostream&,Polynominal&);
    friend istream& operator>>(istream&,Polynominal&);
};//多项式类


Polynominal::Polynominal()//构造函数,构造一个表头结点,形成一个只有表头结点的空链表
{
    head=new struct Term;
    head->next=NULL;
}



Polynominal::~Polynominal()//析构函数,释放多项式各项结点和表头结点
{
    Clear();
    delete head;
    
}

void Polynominal::Clear()//释放多项式各项结点,但保留头结点,得空多项式
{
    Term *q=head,*r;
    for(r=q;r!=NULL;r=q->next)
        q->next=r->next;
    delete r;
}
//..................

void Polynominal::AddTerms(istream& in)
{ 
    Term *q=head;
    float c;
    int e;
    for(;;){
    cout<<"Input a term(coef,exp):"<<endl;
    in>>c>>e;//输入系数c和指数e
    if(e<0)break;//指数为负,退出
    else q=q->InsertAfter(c,e);//构造新项结点<c,e>,插入*q之后,q指向新结点
    }
}

void Polynominal::Output(ostream& out)//输出多项式
{
    Term *q=head;
    out<<"the poltnominal is :"<<endl;
    q=q->next;
    out<<*q;             //第一个结点前不加加号
    for(q=q->next;q!=NULL;q=q->next){
        if(q->coef>0)out<<"+";                
    out<<*q;
    }
    out<<endl;
}


Polynominal& Polynominal::PolyAdd(const Polynominal& x,const Polynominal& y)//多项式加法
{
    Clear();
    Term *p=x.head->next;
    Term *q=y.head->next;
    Term *r=head;
    while(p->exp>=0||q->exp>=0){
    switch(comp(p->exp,q->exp)){
    case -1:
        r=r->InsertAfter(q->coef,q->exp);
        q=q->next;break;
    case 0:
        if(p->coef+q->coef!=0)r=r->InsertAfter(p->coef+q->coef,p->exp);
        p=p->next;q=q->next;
        break;
    case 1:
        r=r->InsertAfter(p->coef,p->exp);
        p=p->next;break;
    }
    }
    return *this;//...........
}

Polynominal& Polynominal::PolyMul(const Polynominal& x,const Polynominal& y)//乘法
{
    Polynominal s,t;
    Clear();
    Term *p,*q=y.head->next;
    for(;q->next!=NULL;q=q->next){//将乘数的每一个项与被乘数多项式相成
        s=x;    //复制被乘数多项式
        for(p=s.head->next;p->next!=NULL;p=p->next){     //s=x*(*q)
            p->coef=p->coef*q->coef;
            p->exp=p->exp+q->exp;
        }
        t=PolyAdd(s,t);  //将多项式的每一个与被乘数多项式相乘的结果累加
    }
    return *this; //*this为乘积多项式
}
Polynominal& Polynominal::PolySub(const Polynominal& x,const Polynominal& y)
{
    Clear();
    Term *p=x.head->next;
    Term *q=y.head->next;
    Term *r=head;
    while(p->exp>=0||q->exp>=0){
    switch(comp(p->exp,q->exp)){
    case 1:
        r=r->InsertAfter(p->coef,p->exp);p=p->next;break;
    case -1:
        r=r->InsertAfter(-(q->coef),q->exp);q=q->next;break;
    case 0:
        /*if(p->coef+q->coef!=0){
            r=r->InsertAfter(p->coef-q->coef,p->exp);
            p=p->next;q=q->next;
        }
        if(p->coef+q->coef==0)p=p->next;q=q->next;*/
        if(p->coef+q->coef!=0)r=r->InsertAfter(p->coef-q->coef,p->exp);
        p=p->next;q=q->next;
        break;
    }
    }
    return *this;//...........
}


int Polynominal::comp(int x,int y){
    if(x==y)return 0;
    else if(x>y)return 1;
    else return -1;
}
ostream& operator<<(ostream&out,Polynominal &x)
{
    x.Output(out);
    return out;
}

istream& operator>>(istream &in,Polynominal &x)
{
    x.AddTerms(in);
    return in;
}

void main()
{
    Polynominal p,q,r;
    cin>>p;cout<<p<<endl;
    cin>>q;cout<<q<<endl;
    cout<<r.PolyAdd(p,q);
    cout<<r.PolyMul(p,q);
    cout<<r.PolySub(p,q);
}
这是我修改后的程序,可是还是有错,输完两个多项式后,它就出来一个框说:什么什么遇到问题需关闭,这是怎么回事??是不是加法乘法程序有问题??
帮忙调试一下.谢谢啦...[em8]