#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
#define  LEN  sizeof(node)
typedef struct polynode   /*用单链表存储多项式的结点结构*/
{
      int coef;  /*多项式的系数*/
      int exp;   /*指数*/
      struct polynode *next; /*next是struct polynode类型中的一个成员，它又指向
                         struct polynode类型的数据，以此建立链表*/
}node;/*若定为"node,*list;"，意即node*与list同为结构指针类型*/
node * create(void)  /*指针函数，返回指针类型；用尾插法建立一元多项式的链表的函数*/
{
     node *h,*r,*s;
     int c,e;
     h=(node *)malloc(LEN);  /*建立多项式的头结点，为头结点分配存储空间*/
     r=h; /*r指针始终动态指向链表的当前表尾，以便于做尾插入，其初值指向头结点*/
     printf("coef:");
     scanf("%d",&c); /*输入系数*/
     printf("exp: ");
     scanf("%d",&e); /*输入指针*/
     while(c!=0)  /*输入系数为0时，表示多项式的输入结束*/
    {
          s=(node *)malloc(LEN); /*申请新结点*/
          s->coef=c;  /*申请新结点后赋值*/
          s->exp=e;   /*申请新结点后赋值*/
          r->next=s; /*做尾插，插入新结点*/
          r=s;  /*r始终指向单链表的表尾*/
          printf("coef:");
          scanf("%d",&c);
          printf("exp: ");
          scanf("%d",&e);
    }
    r->next=NULL; /*将表的最后一个结点的next置NULL，以示表结束*/
    return(h);
}
void polyadd(node *polya, node *polyb)/*一元多项式相加函数，用于将两个多项式相加，然后将和多项式存放在多项式polya中，并将多项式ployb删除*/
{
       node *p,*q,*pre,*temp;
       int sum;
       p=polya->next;/*令p和q分别指向polya和polyb多项式链表中的第一个结点*/
       q=polyb->next;
       pre=polya;    /*位置指针，指向和多项式polya*/
       while(p!=NULL&&q!=NULL) /*当两个多项式均未扫描结束时，执行以下操作*/
      {
            if(p->exp<q->exp)           /*若p指向的多项式指数小于q指的指数*/
            {
                   pre->next=p;      /*将p结点加入到和多项式中*/
                   pre=pre->next;
                   p=p->next;
            }
            else if(p->exp==q->exp)    /*若指数相等，则相应的系数相加*/
            {
                   sum=p->coef+q->coef;
                   if(sum!=0)
                   {
                        p->coef=sum;
                        pre->next=p;pre=pre->next;p=p->next;
                        temp=q;q=q->next;free(temp);
                    }
                  else     /*如果系数和为零，则删除结点p与q，并将指针指向下一个结点*/
                 {
                       temp=p->next;free(p);p=temp;
                       temp=q->next;free(q);q=temp;
                 }
           }
          else                      /*若p指数大于q指数*/
          {
                pre->next=q;  /*p结点不动，将q结点加入到和多项式中*/
                pre=pre->next;
                q=q->next;
          }
    }
    if(p!=NULL)  /*多项式A中还有剩余，则将剩余的结点加入到和多项式中*/
           pre->next=p;
    else        /*否则将B的结点加入到和多项式中*/
           pre->next=q;                                                        
}
void print(node * p) /*输出函数，打印出一元多项式*/
{                                                                                                     
    while(p->next!=NULL)
    {  
        p=p->next;
        printf("     %d*x^%d",p->coef,p->exp);  
         
    }
}  
main()       /*主函数*/
{
      node * polya,* polyb;
      printf("Welcome to use!n");
      printf("nPlease input the ploya include coef && exp:n");
      polya=create();  /*调用建立链表函数，创建多项式A*/
      print(polya);
      printf("nPlease input the ployb include coef && exp:n");
      polyb=create();  /*同理，创建B*/
      print(polyb);
      printf("nSum of the poly is:n");
      polyadd(polya,polyb);    /*调用一元多项式相加函数*/
      print(polya);            /*调用输出函数，打印结果*/
      printf("n");
}