急！！！！！！用c++类实现多项式相加结果出错了 帮忙指示下

[cx968968]

#include <stdlib.h>
#include <stdio.h>
#include<iostream.h>
#include<fstream>
using namespace std;
ifstream in("input.txt");
ofstream out("output.txt");
# define maxsize 100
# define Null 0
class poly
{
private :
int n;
double *p_c;
void set (const double *p_a,int m);
public :
poly () ;
poly (const double *p_a,int m);
poly (const poly &r);
~poly (){delete []p_c;}
int degree ()const {return n;}
void input();
void output() const;
poly &operator = (const poly &r) ;
poly operator + (const poly &r) const;
};
poly::poly()
{

n=0;
p_c=new double[maxsize];

}
void poly::set (const double *p_a,int m)
{
n=m;
int i;
p_c=new double [maxsize];
if (p_c==Null) exit(1);
for (i=0;i<=n;i++)
p_c[i]=p_a[i];
for (i=n+1;i<maxsize;i++)
p_c[i]=0;
}
poly ::poly (const double *p_a,int m)
{
set (p_a,m);
}
poly ::poly (const poly &r)
{
set (r.p_c,r.n);
}
void poly::input()
{
int s,x,m,i,max=0;double c;
in>>x;s=x;
for (i=0;i<maxsize;i++)
p_c[i]=0;
for (i=s;i>0;i--)
{
in>>c>>m;
p_c[m]=c;
max=m>max?m:max;
}
n=max;
}

void poly::output() const
{
poly e(*this);int i,sign=0;
double *a=e.p_c; int b=e.n;
for (i=b;i>=0;i--)
{
if (a[i]==0) continue;
else sign+=1;
if (sign==2) {sign-=1;out<<"+";}
if ((i==1)&&(a[i]!=1)) {out<<a[i]<<"x";continue;}
if ((i==1)&&(a[i]==1)) {out<<"x";continue;}
if (i==0) {out<<a[i];continue;}
if (a[i]==1) {out<<"x^"<<i;continue;}
out<<a[i]<<"x^"<<i;
}
}
poly &poly::operator = (const poly &r)
{
if (p_c!=0) delete []p_c;
p_c=new double [maxsize];
n=r.n;
p_c=r.p_c;
return *this;
}
poly poly::operator +(const poly &r) const
{
poly e(*this);poly a;
int i;
e.n=e.n>r.n?e.n:r.n;
for (i=e.n;i>=0;i--)
e.p_c[i]=e.p_c[i]+r.p_c[i];
return e;
}
int main ()
{
int k,i;
in>>k;
poly *f=new poly[k+1];
char *string=new char [k];
for (i=1;i<k+1;i++)
f[i].input();
f[1].output();
f[2].output();
f[3].output();
f[2]=f[3]+f[1];
f[2].output();
return 0;
}
intput.txt 我的output。txt
3
3 3x^3+4x+6 6x^2+1 3x
3 3 -1.45682e+144x^3+-1.45682e+144x^2+-1.45682e+144x+-1.45682e+144 /就这个输出不对/不知为什么。
4 1
6 0 初学c++；讲详细点；先谢了！
2
6 2
1 0
1
3 1

[cx968968]

谢谢 了 解决了

[太乙]

能不能说下你的input.txt是啥意思？怎么存储的，存储的是啥？

[xuruichen]

[Quote=引用 1 楼 hqin6 的回复:]
能不能说下你的input.txt是啥意思？怎么存储的，存储的是啥？
[/Quote]

楼主你没讲清楚啊！

[cx968968]

第一个3是指3个多项式
3 /这个多项式的项数
33
41 左边这是一个多项式 第一列的3 4 6是系数 第二列是指数（幂） 就是表示3x^3+4x+6
60
下面的数据就跟上面一样的意思
p_c【i】的值是系数 i是指数

[healer_kx]

。。。 。。。
调试啊，都是数字，算呗。

[jakqigle]

两个多项式的系数并行匹配，为相同项的时候其二者系数相加......

[猫已经找不回了]

楼主..你代码这么长,又没注释,好累啊.

[cx968968]

input.txt是个文件 数据要从文件读入 结果输出到output.txt

[lingyin55]

up

[cx968968]

五楼的说的对 就是想这样加

[cx968968]

就是一个类 类的成员函数定义比较长了 辛苦了、忘了注释、

[xtting_8984313]

贴个好点的格式吧，看着头晕。

[cx968968]

#include <stdlib.h>
#include <stdio.h>
#include <iostream.h>
#include <fstream>
using namespace std;
ifstream in("input.txt");
ofstream out("output.txt");
# define maxsize 100
# define Null 0
class poly
{
private :
int n;
double *p_c;
void set (const double *p_a,int m);
public :
poly () ;
poly (const double *p_a,int m);
poly (const poly &r);
~poly (){delete []p_c;}
int degree ()const {return n;}
void input();
void output() const;
poly &operator = (const poly &r) ;
poly operator + (const poly &r) const;
};
poly::poly()
{

n=0;
p_c=new double[maxsize];

}
void poly::set (const double *p_a,int m)
{
n=m;
int i;
p_c=new double [maxsize];
if (p_c==Null) exit(1);
for (i=0;i <maxsize;i++)
p_c[i]=p_a[i];

}
poly ::poly (const double *p_a,int m)
{
set (p_a,m);
}
poly ::poly (const poly &r)
{
set (r.p_c,r.n);
}
void poly::input()
{
int s,x,m,i,max=0;double c;
in>>x;s=x;
for (i=0;i <maxsize;i++)
p_c[i]=0;
for (i=s;i>0;i--)
{
in>>c>>m;
p_c[m]=c;
max=m>max?m:max;
}
n=max;
}

void poly::output() const
{
poly e(*this);int i,sign=0;
double *a=e.p_c; int b=e.n;
for (i=b;i>=0;i--)
{
if (a[i]==0) continue;
else sign+=1;
if (sign==2) {sign-=1;out < <"+";}
if ((i==1)&&(a[i]!=1)) {out < <a[i] < <"x";continue;}
if ((i==1)&&(a[i]==1)) {out < <"x";continue;}
if (i==0) {out < <a[i];continue;}
if (a[i]==1) {out < <"x^" < <i;continue;}
out < <a[i] < <"x^" < <i;
}
}
poly &poly::operator = (const poly &r)
{
if (p_c!=0) delete []p_c;
p_c=new double [maxsize];
n=r.n;
p_c=r.p_c;
return *this;
}
poly poly::operator +(const poly &r) const
{
poly e(*this);poly a;
int i;
e.n=e.n>r.n?e.n:r.n;
for (i=e.n;i>=0;i--)
e.p_c[i]=e.p_c[i]+r.p_c[i];
return e;
}
int main ()
{
int k,i;
in>>k;
poly *f=new poly[k+1];
char *string=new char [k];
for (i=1;i <k+1;i++)
f[i].input();
f[1].output();
f[2].output();
f[3].output();
f[2]=f[3]+f[1];
f[2].output();
return 0;
}

[xtting_8984313]

poly ::poly (const poly &r)
{
set (r.p_c,r.n);
} 

这里有问题，为何没有分配内存呢？

poly  &poly::operator = (const poly &r) 
{
      if (p_c!=0) delete []p_c;
    p_c=new double [maxsize];
      n=r.n;
      p_c=r.p_c;
      return *this;
}

不规范，考虑到异常了吗？应该先new出来，然后swap过去，再删除，看一下effective c++相关条款吧。

[lightnut]

需要修改三个地方

void poly::output() const 
{ 
   out<<"\n";   //<=== 1. 每个poly另起一行输出, 比较清楚

   poly e(*this);int i,sign=0; 
   double *a=e.p_c; int b=e.n; 
   for (i=b;i>=0;i--) 
   { 
      if (a[i]==0) continue; 
      else sign+=1; 
      if (sign==2) {sign-=1;out <<"+";} 
      if ((i==1)&&(a[i]!=1)) {out <<a[i] <<"x";continue;} 
      if ((i==1)&&(a[i]==1)) {out <<"x";continue;} 
      if (i==0) {out <<a[i];continue;} 
      if (a[i]==1) {out <<"x^" <<i;continue;} 
      out <<a[i]  <<"x^" <<i; 
   } 

   
} 

poly  &poly::operator = (const poly &r)  
{ 
   if (p_c!=0) delete []p_c; 
   p_c=new double [maxsize]; 
   n=r.n; 
   for (int i=0; i<maxsize; ++i) {   // <=====2 要copy每一项的系数
      p_c[i]=r.p_c[i]; 
   }
   return *this; 
} 

poly poly::operator +(const poly &r) const 
{ 
   poly e(*this);poly a; 
   int i; 
   e.n=n>r.n?n:r.n;    // <====3 确定最大的x系数 
   for (i=e.n;i>=0;i--) 
      e.p_c[i]=e.p_c[i]+r.p_c[i]; 
   return e; 
}

[cx968968]

不明白 我是先删除原有空间 13楼的能把这段代码改下吗？