用链表实现，设多项式的最高次为N，则申请长度为N的链表对多项式进行存储，之后进行加减时只要把相应的结点相加减即可

#include<iostream>
#include<cstdlib>
using namespace std;

typedef struct Ploynode
{
 int exp;
 double ceof;
 Ploynode *next;
}Ploynode,*Ploylist;


Ploynode* ploycreat()
{
 Ploynode *head,*rear,*s;
 double c;
 int e;
 head=(Ploynode*)malloc(sizeof(Ploynode));
 rear=head;
 cout<<"按照指数的升序输入系数和指数,输入0和0结束:\n";
 cin>>c>>e;
 double EXP=0.00001;
 while(!((c>-EXP)&&(c<EXP)))
 {
  s=(Ploynode*)malloc(sizeof(Ploynode));
  s->ceof=c;
  s->exp=e;
  rear->next=s;
  rear=s;
  cin>>c>>e;
 }
 rear->next=NULL;
 return head;
}

//传递实参的时候ploya的长度>=ployb 
void Ployadd(Ploynode* ploya,Ploynode* ployb)
{
 Ploynode *p,*q,*tail,*temp;
 double sum;
 p=ploya->next;
 q=ployb->next;
 tail=ploya;
 while(p!=NULL&&q!=NULL)
 {
  if(p->exp<q->exp)
  { tail->next=p; tail=p; p=p->next;}
  else if(p->exp==q->exp) 
  {
   sum=p->ceof+q->ceof;
   double EXP=0.00001;
   if(!((sum>-EXP)&&(sum<EXP)))
   {
    p->ceof=sum;
    tail->next=p;
    tail=p;
    p=p->next;
    temp=q; q=q->next; free(temp);
   }
    else 
    {
     temp=p; p=p->next; free(temp);
     temp=q; q=q->next; free(temp);
    }
   }
   else 
   {
    tail->next=q; tail=q;
    q=q->next;
   }
 }//while
  while(p!=NULL)         //把ploya剩余的链接上去 
   {
    tail->next=p;
    tail=p;
    p=p->next;
   }
}
void Output(Ploynode* head)  //打印多项式
{
 Ploynode *p=head->next;
 while(p)
 {
  cout<<p->ceof;
  if(p->exp) cout<<"*x^"<<p->exp;
  if(p->next&&(p->next->ceof)>0) cout<<"+";
  p=p->next;
 }
} 
void  ListDestroy(Ploynode* &L)// 删除所有节点 
 {
    if (!L||!(L->next)) return ;
    Ploynode* p;
    p=L;
    while(L)
      {
        L=p->next;
        free(p);
        p=L;
        cout<<"free memory"<<endl;
      }
 } 
int main()
{
 Ploynode *ploya=ploycreat();
 cout<<"\n Ploynode A:\n";
 Output(ploya);
 cout<<endl;
 Ploynode *ployb=ploycreat();
 cout<<"\n Ploynode B:\n";
 Output(ployb);
 cout<<endl;
 Ployadd(ploya,ployb);
 cout<<"Ploy A + B = \n";
 Output(ploya);
 cout<<endl;
 ListDestroy(ploya);
 
 system("pause");
 return 0;
}
 
 
 我还写过相乘的，不过是用STL 做的