C语言链表实现多项式加法乘法

数据结构（浙大版）
多项式
小记

#include<stdio.h>
#include<stdlib.h>
typedef struct PolyNode *Polynomial;
struct PolyNode
{
	int coef;
	int expon;
	Polynomial link;
};
int Compare(int P1, int P2) {
	if (P1 > P2) return (1);
	else if (P1 < P2) return (-1);
	return (0);
}
void Attach(int c, int e, Polynomial *pRear) {
	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;
	*pRear = P;//修改pRear值
}
Polynomial ReadPoly() {
	Polynomial P, Rear, t;
	int N,c,e;
	scanf_s( "%d",&N);
	P = (Polynomial)malloc(sizeof(struct  PolyNode));/*链表头空结点*/
	P->link = NULL;
	Rear = P;
	while (N--)
	{
		scanf_s("%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);//删除临时创建的头节点
	return P;
}
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)
	{/*先用P1的第1项乘以P2，得到P*/
		Attach(t1->coef*t2->coef, t1->expon + t2->expon, &Rear);
		t2 = t2->link;
	}
	t1 = t1->link;
	while (t1)
	{
		t2 = P2; Rear = P;
		while (t2){
			c = t1->coef*t2->coef;
			e=t1->expon + t2->expon;
			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;
			}
		t1 = t1->link;
	}
	t2 = P; P = P->link; free(t2);
	return P;
}
void PrintPoly(Polynomial P) {/*输出多项式*/
	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("%-3dX^%-2d", P->coef, P->expon);
		P = P->link;
	}
	printf("\n");
}
Polynomial Add(Polynomial P1, Polynomial P2) {
	Polynomial front, rear, temp;
	int sum;
	rear = (Polynomial)malloc(sizeof(struct PolyNode));
	front = rear;//有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需要处理时
		switch (Compare(P1->expon, P2->expon))
		{
		case 1:
			Attach(P1->coef, P1->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;
		}
	/*将未处理完的另一个多项式的
	所有节点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;//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;
}
int main()
{
	Polynomial P1, P2, PP, PS;
	P1 = ReadPoly();
	P2 = ReadPoly();
	PP = Mult(P1, P2);
	PrintPoly(PP);
	PS = Add(P1, P2);
	PrintPoly(PS);
}