用插入法实现多项式的乘法

#include"iostream"
#include"stdio.h"
#include"string.h"
#include"algorithm"
#include"queue"
#include"stack"
#include"ctype.h"
#include"cmath"
#define mx 1005
using namespace std;

struct poly //链表节点数据类型
{
    double ceof;//系数
    int exp;//指数
    poly *next;
};
double A[mx],B[mx];//存放A和B表达式
int adegree,bdegree,maxexp;//存放最高阶数

void init(poly *&pl) //链表初始化
{
    pl=new poly;//动态分配空间，如果出现错误则输出 allocate error
    if(pl==NULL){cout<<"allocate error!"<<endl;}
    else
    {
        pl->next=NULL;
    }
}

void input(poly *&pl,int degree,double X[]) //表达式的输入（存入链表中）
{
    poly *t=pl;
    int i=0;
    while(i<=degree)
    {
        if(X[i]!=0) //系数为零的不用存
        {
            t->next=new poly;
            t=t->next;
            t->ceof=X[i];
            t->exp=i;
        }
        i++;
    }
    t->next=NULL;
}

void output(poly *&pl) //表达式的输出
{
    poly *t=pl->next;
    cout<<"the polynomal is:";
    bool h=true;
    while(t!=NULL)
    {
        if(!h) cout<<"+";
            h=false;
        if(t->ceof!=1||t->exp==0)
        cout<<t->ceof;
        switch(t->exp) //根据阶数输出相应的项
        {
            case 0:break;
            case 1:cout<<"x";break;
            default:cout<<"x^"<<t->exp;
        }
        t=t->next;
    }
    cout<<endl;
}

void insert_poly(poly *&pl,double ceof_,int exp_)
{
    poly *t,*pre,*newpoly;
    t=pl->next;pre=pl;
    while(t!=NULL&&t->exp>exp_)
    {
         pre=t;
        t=t->next;
    }
    if(t!=NULL&&t->exp==exp_)
    {
        t->ceof+=ceof_;
        if(t->ceof==0)//如果多项式系数为零，则删除
        {
            pre->next=t->next;
            delete t;
        }
    }
    else
    {
        newpoly=new poly;
        newpoly->ceof=ceof_;
        newpoly->exp=exp_;
        pre->next=newpoly;
        newpoly->next=t;
    }
}
void mul_poly(poly *&pla,poly *&plb,poly *&plc) //用插入法实现表达式相乘
{
    poly *ta,*tb;
    if(adegree!=-1&&bdegree!=-1) //没有零多项式，执行相乘运算
    {
        ta=pla->next;
        while(ta!=NULL)//模拟笔算多项式相乘
        {
            tb=plb->next;
            while(tb!=NULL)
            {
                insert_poly(plc,(ta->ceof)*(tb->ceof),ta->exp+tb->exp);
                tb=tb->next;
            }
            ta=ta->next;
        }
    }
}
int main()
{
    poly *pla,*plb,*plc;
    int i,j,_exp;
    double _ceof;
    char ch;
    int case_=0;
    while(++case_)
    {
        cout<<"case "<<case_<<":"<<endl;
        memset(A,0,sizeof(A));
        memset(B,0,sizeof(B));
        init(pla);//初始化，这个操作一定要有
        init(plb);
        init(plc);
        ch='0';
        cout<<"input A poly:";
        while(ch!='\n')//A表达式的输入
        {
            cin>>_ceof;
            getchar();getchar();
            cin>>_exp;
            ch=getchar();
            A[_exp]=_ceof;
            adegree=_exp;
        }
        input(pla,adegree,A);
        cout<<"input B poly:";
           ch='0';
        while(ch!='\n')//B表达式的输入
        {
            cin>>_ceof;
            getchar();getchar();
            cin>>_exp;
            ch=getchar();
            B[_exp]=_ceof;
            bdegree=_exp;
        }
        input(plb,bdegree,B);
        mul_poly(pla,plb,plc);
        output(plc);//输出最终结果
        cout<<"insert one formula to the poly:";
            cin>>_ceof;
            getchar();getchar();
            cin>>_exp;
        insert_poly(plc,_ceof,_exp);
        output(plc);//输出插入一项后的最终结果
        cout<<endl;
    }
}