表达式求解

//数据结构 实验一#includeusing namespace std;struct unit{float coef;  // 系数int expn;    // 指数};typedef struct polynomial{unit e;polynomial *next;polynomial *head;}*P;int cmp(unit a,unit b);void CreatePolyn(P &p,int m);void print(P &ha);void AddPolyn(P &Pa,P &Pb);int main(){P Pa,Pb;int m;cout<<"输入表达式Pa的项数:"<<endl;cin>>m;cout<<"输入表达式Pa的各项(按指数的从大到小的顺序):"<<endl;CreatePolyn(Pa,m);cout<<"输入表达式Pb的项数："<<endl;cin>>m;cout<<"输入表达式Pb的各项(按指数的从大到小的顺序):"<<endl;CreatePolyn(Pb,m);AddPolyn(Pa,Pb);cout<<"结果如下:"<<endl;print(Pa);}int cmp(unit a,unit b){if(a.expn > b.expn)return -1;else if(a.expn == b.expn)return 0;else if(a.expn < b.expn)return 1;}void CreatePolyn(P &p,int m){p = new polynomial;p->next = NULL;p->head = p;p->e.coef = 0.0;p->e.expn = -1;int i;P now;for (i = 1;i <= m;i++){float coef;int expn;cin>>coef>>expn;P s;s = new polynomial;s->e.coef = coef;s->e.expn = expn;if(i==1){s->next= p->next;p->next= s;}else{s->next= now->next;now->next = s;}s->head = p;now = s;}}void print(P &ha){for(P i =ha->head->next;i;i = i->next){if(!i->next){cout<<i->e.coef<<""<<i->e.expn<<endl;break;}cout<<i->e.coef<<""<<i->e.expn<<",";}}void AddPolyn(P &Pa,P &Pb){P ha,hb,qa,qb;unit a,b;ha = Pa->head;hb = Pb->head;qa = Pa->next;qb = Pb->next;while(qa && qb){float sum;a = qa->e;b = qb->e;switch(cmp(a,b)){case -1:   //a > bha = qa;qa = qa->next;break;case 0:sum = a.coef + b.coef;if(sum != 0.0){qa->e.coef = sum;ha = qa;}else{//删除PA中当前结点ha->next = qa->next;//释放空间delete qa;}hb->next = qb->next;delete qb;qb = hb->next;qa = ha->next;break;case 1:hb->next = qb->next;qb->next = ha->next;ha->next = qb;qb = hb->next;ha = ha->next;break;}}if(Pb->head->next)ha->next = qb;//链接剩余节点delete hb;}