软件工程（2019）第一次结队作业程序

#include<stdio.h>
#include<stdlib.h>

typedef struct term{//项的表示
    float coef;//系数
    int expn;//指数
    struct term *next,*pre;
}*ElemType;

void createPolyn(ElemType &polyn)//创建一个多项式链表
{
    polyn=(ElemType)malloc(sizeof(term));
    ElemType q,p;
    p=polyn;
    polyn->next=q;
    polyn->pre=NULL;
    q->next=NULL;
    q->pre=polyn;
    for(int i=1;;i++)
    {
        q=(ElemType)malloc(sizeof(term));
        printf("请输入第%d项系数和指数:",i);
        scanf("%f%d",&q->coef,&q->expn);
        p->next=q;
        q->pre=p;
        q->next=NULL;
        if(q->coef==0 && q->expn==0)
            break;
        p=q;
    }
}

void addPolyn(ElemType &p1,ElemType &p2)//多项式相加
{
    ElemType polyn1=p1->next,polyn2=p2->next;
    while(polyn1->next&&polyn2->next)
    {
        if(polyn2->expn > polyn1->expn)
            polyn1=polyn1->next;
        else if(polyn2->expn == polyn1->expn)
        {
            polyn1->coef+=polyn2->coef;
            polyn1=polyn1->next;
            polyn2=polyn2->next;
            free(polyn2->pre);
        }
        else if(polyn2->expn < polyn1->expn)
        {
            ElemType pp=polyn2->next;
            polyn1->pre->next=polyn2;
            polyn2->next=polyn1;
            polyn2->pre=polyn1->pre;
            polyn1->pre=polyn2;
            polyn2=pp;
        }
    }
    while(polyn2->next)
    {
        polyn1->next=polyn2;
        polyn1=polyn1->next;
        polyn2=polyn2->next;
    }
}

void subPolyn(ElemType &p1,ElemType &p2)
{
    ElemType polyn1=p1,polyn2=p2;
    while(polyn1->next&&polyn2->next)
    {
        if(polyn2->expn > polyn1->expn)
            polyn1=polyn1->next;
        else if(polyn2->expn == polyn1->expn)
        {
            polyn1->coef-=polyn2->coef;
            polyn1=polyn1->next;
            polyn2=polyn2->next;
            free(polyn2->pre);
        }
        else if(polyn2->expn < polyn1->expn)
        {
            ElemType pp=polyn2->next;
            polyn1->pre->next=polyn2;
            polyn2->next=polyn1;
            polyn2->pre=polyn1->pre;
            polyn1->pre=polyn2;
            polyn2=pp;
        }
    }
}

void printPolyn(ElemType polyn)//打印多项式
{
    ElemType p;
    p=polyn->next;
    for(int i=1;p->next!=NULL;i++)
    {
        if(p->coef>0 && i!=1 && p->expn!=0)
            printf("+%.2fx^%d",p->coef,p->expn);
        else if(p->coef<0 && p->expn!=0)
            printf("%.2fx^%d",p->coef,p->expn);
        else if(p->coef>0 && i==1 && p->expn!=0)
            printf("%.2fx^%d",p->coef,p->expn);
        else if(p->coef>0 && i!=1 && p->expn==0)
            printf("+%.2f",p->coef);
        else if(p->coef<0 && p->expn==0)
            printf("%.2f",p->coef);
        else if(p->coef>0 && i==1 && p->expn==0)
            printf("%.2f",p->coef);
        p=p->next;
    }
    printf("\n");
}

int main()
{
    ElemType polyn1,polyn2;
    printf("请输入第一个多项式\n");
    createPolyn(polyn1);
    printPolyn(polyn1);
    printf("请输入第二个多项式\n");
    createPolyn(polyn2);
    printPolyn(polyn2);
    printf("两个多项式相加\n");
    addPolyn(polyn1,polyn2);
    printPolyn(polyn1);
    printf("两个多项式相减\n");
    subPolyn(polyn1,polyn2);
    printPolyn(polyn1);
    return 0;
}