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
*/