一元多项式的相乘

#include <iostream>
#include<stdlib.h>

using namespace std;


#define MAXSIZE 20

typedef struct LNode
{
    int coef;//系数
    int expn;//指数
    struct LNode *next;
}LNode,*LinkList;


int CreateList_L(LinkList &L,int n)
{
    LinkList p,q;
    for(int i=0;i<n;i++)
    {
         p=(LinkList)malloc(sizeof(LNode));
         cout<<"输入元素系数：";
         cin>>p->coef;
         cout<<"输入元素指数：";
         cin>>p->expn;
         if(i==0)L=p;
         else q->next=p;
         q=p;
         p->next=NULL;
    }
   return 0;
}


int LengthPolyn(LinkList L)//判断多项式的项数
{
    int s=0;
    while(L)
    {
        s++;
        L=L->next;
    }
    return s;
}


int CopyList_L(LinkList La,LinkList &Lb)//开辟一段和La指向的空间一样的新的空间，并把La中各元素的值依次复制到Lb中
{
    LinkList p,q,pa=La;
    int n=LengthPolyn(La);
    for(int i=0;i<n;i++)
    {
         p=(LinkList)malloc(sizeof(LNode));
         p->coef=pa->coef;
         p->expn=pa->expn;
         if(i==0)Lb=p;
         else q->next=p;
         q=p;
         p->next=NULL;
         pa=pa->next;
    }
   return 0;
}



int Display_L(LinkList L)
{
    cout<<"f(x)="<<L->coef;
    if(L->expn)cout<<"*"<<"x^"<<L->expn;
    L=L->next;
    while(L)
    {
        if(L->coef>0)
        {
            cout<<"+";
            cout<<L->coef<<"*"<<"x^"<<L->expn;
        }
        else cout<<L->coef<<"*"<<"x^"<<L->expn;
        L=L->next;
    }
    return 0;
}



int AddPolyn(LinkList La,LinkList Lb,LinkList &Lc)
{
    LinkList pa,pb,p;
    int k=1;
    pa=La;pb=Lb;
    //确定“和多项式”的头结点
    while(k)
    {
         if(pa->expn<pb->expn){p=Lc=pa;pa=pa->next;k=0;}
         else if(pa->expn>pb->expn){p=Lc=pb;pb=pb->next;k=0;}
         else
         {
             pa->coef+=pb->coef;
             if(pa->coef)
             {
                  p=Lc=pa;
                  pa=pa->next;
                  k=0;
             }
             else
             {
                 pa=pa->next;
                 pb=pb->next;
                 if(!pa||!pb) break;
             }
         }
    }
    if(!pb&&pa){p=Lc=pa;pa=pa->next;}
    if(!pa&&pb){p=Lc=pb;pb=pb->next;}
    if(!pa&&!pb) Lc=NULL;
    //确定接下来的节点
    while(pa&&pb)
    {
        if(pa->expn<pb->expn){p->next=pa;p=pa;pa=pa->next;}
        else if(pa->expn>pb->expn){p->next=pb;p=pb;pb=pb->next;}
        else
        {
            pa->coef+=pb->coef;
            if(pa->coef)
            {
                  p->next=pa;
                  p=pa;
                  pa=pa->next;
                  pb=pb->next;
            }
            else
            {
                  pa=pa->next;
                  pb=pb->next;
            }

        }
    }
    while(!pb&&pa)
    {
        p->next=pa;
        p=pa;
        pa=pa->next;
    }
    while(!pa&&pb)
    {
        p->next=pb;
        p=pb;
        pb=pb->next;
    }
    return 0;
}



int MultiplyPolyn(LinkList La,LinkList Lb,LinkList &Lc)//La指向的多项式乘以Lb指向的多项式
{
    LinkList pa,pb=Lb,l;
    int i=0,j,n;
    LNode *L[MAXSIZE];//指针数组，Lb至多MAXSIZE项！
    while(pb)
    {
        CopyList_L(La,L[i]);
        pa=L[i];
        while(pa)
        {
            pa->coef*=pb->coef;
            pa->expn+=pb->expn;
            pa=pa->next;
        }
        pb=pb->next;
        i++;
    }
    n=LengthPolyn(Lb);
    AddPolyn(L[0],L[1],Lc);
    for(j=2;j<n;j++)
    {
        AddPolyn(L[j],l,Lc);
        l=Lc;
    }
    return 0;
}



int main()
{
    LinkList La,Lb,Lc;
    int m,n;
    cout<<"请输入La中的元素个数：";
    cin>>m;
    CreateList_L(La,m);
    cout<<"请输入Lb中的元素个数：";
    cin>>n;
    CreateList_L(Lb,n);
    MultiplyPolyn(La,Lb,Lc);
    Display_L(Lc);
    return 0;
}