数据结构——多项式相加

#include <iostream>
using namespace std;

struct linkpolyn
{
    int coef;
    int expn;
    struct linkpolyn * next;
};
typedef struct linkpolyn LinkPolyn;

//创建链表函数
LinkPolyn *Creat()
{
    LinkPolyn *h,*p;
    h=(LinkPolyn *) malloc(sizeof(LinkPolyn));
    h->next=NULL;
    LinkPolyn *temp;
    temp=h;
    cout<<"请输入: "<<endl;
    do
    {
        p=(LinkPolyn *) malloc(sizeof(LinkPolyn));    //给第一个节点分配内存
        cin>>p->coef>>p->expn;
        if(p->coef == 0 && p->expn==0)
            break;
        p->next=temp->next;
        temp->next=p;
        temp=p;
    }while(1);    //以0结束输入
    return h;
}//end creat

//打印输出函数
void PrintPolyn(LinkPolyn *h)
{
    LinkPolyn * p1;
    p1=h->next;
    if(h->next==NULL)
    {
        cout<<"Polyn is empty!"<<endl;
    }
    else
    {
        while(p1!=NULL)
        {
            cout<<p1->coef<<"x^"<<p1->expn<<"+";
            p1=p1->next;
        }
        cout<<"end"<<endl;
    }
}//end printPolyn


//表达式相加
LinkPolyn *  add_Polyn(LinkPolyn *  ha , LinkPolyn * hb)
{
    LinkPolyn * pa,* pb;
    pa=ha->next;
    pb=hb->next;
    LinkPolyn * prea, *preb;
    prea=ha;
    preb=hb;

    while(pa && pb)
    {
        if(pa->expn < pb->expn)
        {
            prea=pa;
            pa=pa->next; 
        }
        else if(pa->expn == pb->expn)
        {
            if(pa->coef + pb->coef !=0)
            {
                pa->coef += pb->coef;
                prea=pa;
            }
            else
            {
                prea->next=pa->next;
            }
            preb->next=pb->next;
            pa=pa->next;
            pb=pb->next;
        }    
        else
        {
            preb->next=pb->next;
            pb->next=pa;
            prea->next=pb;

            pb=preb->next;
            prea=prea->next;
        }
    }

    if(pb)    //讲多项式B中未完成的链接到A山去
    {
        prea->next=pb;
    }
    return ha;
}

int main()
{
    LinkPolyn *head1;

    //创建多项式1
    head1=Creat();        //head1接受返回的指向头结点指针
    PrintPolyn(head1);

    //创建多项式2
    LinkPolyn *head2;
    head2=Creat();        //head1接受返回的指向头结点指针
    PrintPolyn(head2);

    //多项式相加
    LinkPolyn *head3;
    head3=add_Polyn(head1 , head2);    //指针要更新
    PrintPolyn(head3);    //输出相加后的表达式
    return 0;
}