此一元多项式错在哪？？？

hua_zhixing_ 2009-04-12 12:46:01

#include<iostream>

using namespace std;



typedef struct sterm{//项的表示，多项式的项作为polynomial的数据元素

	int coef;

	int expn;

	sterm *next;

}term,*polynomial;



term *creat(int n){//按从头到尾的顺序创建带关结点的单链表存储多项式

	term *head,*p,*q;

    //int  s;

    head=(polynomial)malloc(sizeof(term));//先建立一个带头结点的单链表

    head->next=NULL;

    head->coef=0;

    head->expn=-1;

    q=head;

	

	for(int i=n;i>0;i--){

        p=(polynomial)malloc(sizeof(term));//生成新结点

		cin>>p->coef>>p->expn;//输入元素值

		q->next=p;

		p->next=NULL;

		q=p;//插入到表尾

	}

	return head;

}



void print(polynomial head){//以表达式的形式输出存储在链表中的多项式

	term *p;

	p=head->next;

	cout<<p->coef<<"x^"<<p->expn;

	p=p->next;

	while(p){

		if(p->coef>0)

			cout<<"+"<<p->coef<<"x^"<<p->expn;

		else 

			if(p->coef<0)

				cout<<p->coef<<"x^"<<p->expn;

		p=p->next;

	}

	cout<<endl;

}



polynomial addpolyn(polynomial f,polynomial g){//实现两个多项式相加

	polynomial p,q,pre,u;

	int sum;

	p=f;//f;

	q=g;

	pre=f;

	while(p!=NULL && q!=NULL){

		if(p->expn<q->expn){//p指针所指项的指数小于q指针所指项的指数，p往后移

			   pre=p; p=p->next;

		}

		else  if(p->expn==q->expn){//p指针所指项的指数等于q指针所指项的指数，相加，

			          sum=p->coef+q->coef;  //并将结果（不为零）存入p指针所指系数域中

			          if(sum!=0){

				         p->coef=sum;

						 pre=p; 

					  }

			          else{ pre->next=p->next;  free(p);}

		   }

		   else{//p指针所指项的指数大于q指针所指项的指数，q指针所指项插入到p所指项之前

			   u=q->next; 

			   q->next=p;

			   pre->next=q;

			   pre=q;

			   q=u;

			}

	}

	if(q!=NULL)  pre->next=q;//q指针未到g链表末尾，将其链接到f链表后面

	free(g);

	return f;

}



polynomial reverse(polynomial l){//实现两个多项式带关结点的单琏表的逆置，

	polynomial p,q;              //仿照从表尾到表头逆向建立单链表的算法

	p=l->next;

	l->next=NULL;

	while(p){

		q=p->next;

		p->next=l->next;

		l->next=p;

		p=q;

	}

	return l;

}



polynomial multiply(polynomial f,polynomial g){

	polynomial h,l,fp,gp,hp,q;//实现两个多项式相乘，将一个多项式按指数从高

	int max,k,r;              //到低排序，另一个多项式按指数从低到高排序

	int c;

	max=25;

	max=f->expn+g->expn;

	h=(term*)malloc(sizeof(term));

	h->coef=0;

	h->expn=-1;

	h->next=NULL;

	hp=h;

	l=reverse(g);

	for(r=max;r>=0;r--){

		c=0;

		fp=f->next;

		gp=l->next;

		while(fp&&gp){

			k=fp->expn+gp->expn;

			if(k>r)

				fp=fp->next;

			else if(k<r)

				gp=gp->next;

			else{

				c+=fp->coef*gp->coef;

				fp=fp->next;

				gp=gp->next;

			}

		}

		if(c!=0){

			q=(term*)malloc(sizeof(term));

			q->expn=r;

			q->coef=c;

			q->next=hp->next;

			hp->next=q;

			hp=q;

		}

	}

	return h;

}



int main(){

	polynomial e,f,g,h;

	int n,m;



    cout<<"n=";

    cin>>n;

	f=creat(n);



	cout<<"m=";

	cin>>m;

	g=creat(m);



	e=addpolyn(f,g);

	print(e);

	f=reverse(f);

	h=multiply(f,g);

	print(h);



	return 1;

}