两个多项式相加及相乘

#include <stdio.h>
#include <malloc.h> 

 typedef struct PolyNode *Polynomial;
 struct PolyNode{
    int coef;
    int expon;
    Polynomial link;
 };

 void Attach(int c,int e,Polynomial *pRear) //pRear是指针的指针 
 {
    Polynomial P;

    P=(Polynomial)malloc(sizeof(struct PolyNode));
    P->coef=c; //对新结点赋值 
    P->expon=e;
    P->link=NULL;
    (*pRear)->link=P; //修改pRear的值 
    *pRear=P;
 }
 Polynomial ReadPoly()
 {
    Polynomial P,Rear,t;
    int c,e,N;

     scanf("%d",&N);
     P=(Polynomial)malloc(sizeof(struct PolyNode)); //链表头空结点 
     P->link=NULL;
     Rear=P;
    while(N--){
        scanf("%d%d",&c,&e);
        Attach(c,e,&Rear); //将当前项插入多项式尾部 

     }
     t=P;P=P->link;free(t); //删除临时生成的头结点 
     return P;
 }

 Polynomial Add(Polynomial P1,Polynomial P2)
 {
    Polynomial front,rear,temp;
    int sum;
    rear=(Polynomial)malloc(sizeof(struct PolyNode));
    front=rear; /*由front记录结果多项式链表头结点*/
    while(P1&&P2){ /*当两个多项式都有非零项待处理时*/ 
        if(P1->expon==P2->expon){
            sum=P1->coef+P2->coef;
            if(sum){
            Attach(sum,P1->expon,&rear);
            P1=P1->link;
            P2=P2->link;

            }else{
                P1=P1->link;
                P2=P2->link;

             }
         }else if(P1->expon>P2->expon){
            Attach(P1->coef,P1->expon,&rear);
            P1=P1->link;
         }else{
            Attach(P2->coef,P2->expon,&rear);
            P2=P2->link;
         }
     }
     /*将未处理完的另一个多项式的所有节点依次复制到结果多项式中去*/ 
     while(P1){
        Attach(P1->coef,P1->expon,&rear);
        P1=P1->link;
     }
     while(P2){
        Attach(P2->coef,P2->expon,&rear); 
        P2=P2->link;
     }
    rear->link=NULL;
    temp=front;
    front=front->link; /*令front指向结果多项式第一个非零项*/ 
    free(temp);        /*释放临时空表头结点*/ 
    return front;
  } 

/*采用逐项插入的方法，将P1当前项乘以P2的当前项，并插入到结果多项式中，关键是要找到插入的位置*/  
/*初始结果多项式由P1第一项乘以P2各项获得*/ 
Polynomial Mult(Polynomial P1,Polynomial P2)
{
    Polynomial P,Rear,t1,t2,t;
    int c,e;

    if(!P1||!P2){
        return NULL;
    }
    t1=P1;t2=P2;
    P=(Polynomial)malloc(sizeof(struct PolyNode));P->link=NULL;
    Rear=P;
    while(t2){ //P1第一项乘以P2各项得到初始结果多项式 
        Attach(t1->coef*t2->coef,t1->expon+t2->expon,&Rear);

        t2=t2->link;
    }
    t1=t1->link;
    while(t1){
        t2=P2;Rear=P;

        while(t2){
            e=t1->expon+t2->expon;
            c=t1->coef*t2->coef;
            while(Rear->link&&Rear->link->expon>e)
            Rear=Rear->link;
            if(Rear->link&&Rear->link->expon==e){
                if(Rear->link->coef+c)
                 Rear->link->coef+=c;
                else{
                    t=Rear->link;
                    Rear->link=t->link;
                    free(t);
                }
            }
            else{
                t=(Polynomial)malloc(sizeof(struct PolyNode));
                t->coef=c;
                t->expon=e;
                t->link=Rear->link;
                Rear->link=t;
                Rear=Rear->link;
            }
            t2=t2->link;
            //printf("%d,%d\n",Rear->coef,Rear->expon);


        }
        t1=t1->link; 
    }
    t2=P;P=P->link;free(t2);
    return P;

}

 void PrintPoly(Polynomial P)
 {
    int flag=0;  //辅助调整输出格式用 
    if(!P){
        printf("0 0\n");
         return;
     } 
     while(P){
        if(!flag)
         flag=1;
        else 
          printf(" ");
          printf("%d %d",P->coef,P->expon);
          P=P->link;
     }
 } 
 int main()
 {
    Polynomial P1,P2,PS,PP;
    P1=ReadPoly();

    P2=ReadPoly();

    PP=Mult(P1,P2);
    PrintPoly(PP);
    printf("\n");
    PS=Add(P1,P2);
    PrintPoly(PS); 

    return 0;
 }

/* 测试数据
4 3 5 2 4 3 3 6 1
3 2 5 3 4 4 3
*/