ex4.cpp

来自「上海交通大学本科算法大作业」· C++ 代码 · 共 156 行

#include<iostream>
#include<sstream>
#include<string>
#include<fstream>
using namespace std;
struct polynode
{
    polynode *next;
    int a,e;//ax^e
};
class poly
{
protected:
    polynode *head,*tail;
    void additem(int a,int e);
    void add(int,int);
public:
    poly(){head=tail=NULL;};
    poly(char*,int);
    poly(poly&);
    ~poly();
    void display();
    friend void operator*(poly&,poly&);
};
void poly::additem(int a,int e)
{
    polynode *p=new polynode;
    p->a=a;
    p->e=e;
    p->next=NULL;
    if(tail==NULL)
    {
        head=p;
    }
    else
    {
        tail->next=p;
    }
    tail=p;
}
poly::poly(char *str, int n)
{
    char *prestr;
    int t,a;
    t = n;
    head=tail=NULL;
    istringstream stream(str);
    while(stream >> a)
            additem(a,t--);
    return;
}
poly::poly(poly& t)
{
    polynode *p;
    if((p=t.head)==NULL)
    {
        head=tail=NULL;
        return;
    }
    head=tail=new polynode;
    head->a=p->a;
    head->e=p->e;
    head->next=NULL;
    p=p->next;
    while(p)
    {
        add(p->a,p->e);
        p=p->next;
    }
}
poly::~poly()
{
    polynode *p=head,*prep;
    while(p)
    {
        prep=p;
        p=p->next;
        delete prep;
    }
}
void poly::display()
{
    polynode *p=head;
    ofstream fout("result1.txt"); 
    while(1)
    {
        fout<<p->a;
        p=p->next;
        if(p)fout<<" ";
        else break;
    }
    fout<<endl;
    fout.close();
}
void poly::add(int a,int e)
{
    polynode *p=head;
    if(p==NULL)
    {
        head=tail=new polynode;
        tail->a=a;
        tail->e=e;
        tail->next=NULL;
    }
    else
    {
        while(p&&p->e!=e)p=p->next;
        if(p==NULL)
        {
            p=new polynode;
            p->a=a;
            p->e=e;
            p->next=NULL;
            tail->next=p;
            tail=p;
        }
        else
        {
            p->a+=a;
        }
    }
}
void operator*(poly& f1,poly& f2)
{
    int a,e;
    poly rst;
    polynode *p,*q;
    if(f1.head==NULL||f2.head==NULL)
    {
        poly tmp("0",0);                           
        return  ;
    }
    for(p=f1.head;p!=NULL;p=p->next)
        for(q=f2.head;q!=NULL;q=q->next)
        {
            a=p->a*q->a;
            e=p->e+q->e;
            rst.add(a,e);
        }
    rst.display();
}
int main()
{
    char str1[255],str2[255];
    int n;
    ifstream fin("data1.txt"); 
    fin >> n ;
    fin.getline(str1,255);
    fin.getline(str1,255);
    fin.getline(str2,255);
    poly a(str1,n),b(str2,n);
    a*b;
    fin.close();
    return 0;
}