多项式加法运算

2.4 多项式加法运算

struct PolyNode{
	int coef;/*系数*/
	int expon;/*指数*/
	struct PolyNode *link;/*指向下一结点的指针*/
};
typedef struct PolyNode *Polynomial;
Polynomial P1,P2;

Polynomial PolyAdd(Polynomial P1,Polynomial P2)
{
	Polynomial front,rear,temp;
	int sum;
	rear = (Polynomial)malloc(sizeof(struct PolyNode));
	front = rear;/*由front记录结果多项式头结点*/

	while(P1&&P2)
		switch(Compare(P1->expon,P2->expon)){
			case 1:
				Attach(P1->coef,P2->expon,&rear);
				P1 = P1->link;
				break;
			case -1:
				Attach(P2->coef,P2->expon,&rear);
				P2 = P2->link;
				break;
			case 0:
				sum = P1->coef + P2->coef;
				if(sum) Attach(sum,P1->expon,&rear);
				P1 = P1->link;
				P2 = P2->link;
				break;
		}
	/*将未处理完的多项式依次复制到结果多项式中去*/
	for(;P1;P1=P1->link) Attach(P1->coef,P1->expon,&rear);
	for(;P2;P2=P2->link) Attach(P2->coef,P2->expon,&rear);
	rear->link = NULL;
	temp = front;
	front = front->link;/*使front指向多项式第一个非零项*/
	free(temp);/*释放临时空表头结点*/
	return front;
}

void Attach(int c,int e,Polynomial *pRear)
{
	Polynomial P;
	
	P = (Polynomial)malloc(sizeof(struct Polynomial));/*申请新结点*/
	P->coef = c;/*对新结点赋值*/
	P->expon = e;
	P->link = NULL;
	/*将P指向的新结点插入到当前多项式结尾的后面*/
	(*pRear)->link = P;
	*pRear = P; 	
}