问题描述：
6-3 【CPP0024】设计并实现大数类BigNum 分数 10 作者 C++多态编程 单位 石家庄铁道大学定义一个整数型大数类，要求能够完成100位以内的较大整数的加法和减法计算，main(void)函数完成对其的测试。
BigNum类结构说明：
BigNum类的数据成员包括：
①私有数据成员：数值域num(char []型)。
BigNum类成员函数包括：
①有参构造函数BigNum(char c[])和拷贝构造函数BigNum(const BigNum &)，其中有参构造函数参数默认值为"+0"，输出信息"BigNum Constructor run"，拷贝构造函数输出信息"BigNum CopyConstructor run"
②析构函数，析构函数输出信息"BigNum Destructor run"
③公有函数成员void setNum(char c[])和char const *getNum(void) const分别返回和设置数值域。
④重载“+”运算符，实现两个BigNum对象相加的运算
⑤重载“-”运算符，实现两个BigNum对象相减的运算
⑥公有成员函数void show() const用于显示BigNum对象的信息，显示格式为：BigNum(<数值域>)
建议：大数存储时专门存储符号位且低位存储在前，高位存储在后。这样便于运算实现。
裁判测试程序样例：
#include <iostream>
using namespace std;
#define N 100
/*请在这里填写答案*/
//主函数
int main(void){
char c[100],op;
cin>>c;
BigNum b1(c),b2(b1);
b1.show();
cin>>c;
b2.setNum(c);
b2.show();
cin>>op;
if(op=='+') (b1+b2).show();
if(op=='-') (b1-b2).show();
return 0;
}
输入样例：
123
234
-
输出样例：
BigNum Constructor run
BigNum CopyConstructor run
BigNum(+123)
BigNum(+234)
BigNum Constructor run
BigNum CopyConstructor run
BigNum Destructor run
BigNum(-111)
BigNum Destructor run
BigNum Destructor run
BigNum Destructor run
代码：#include<cstring>
class BigNum
{
private:
char num[N];
public:
BigNum( char c[N] = "+0" );
BigNum( const BigNum &p );
~BigNum()
{
cout<<"BigNum Destructor run"<<endl;
}
void setNum( char c[N] );
char const * getNum(void) const;
BigNum operator + ( const BigNum &a );
BigNum operator - ( BigNum &b );
void show() const;
};
BigNum::BigNum( char c[N] )
{
int i,j,a = strlen(c);
if( c[0] != '-')
{
num[0] = '+';
if( c )
{
for( i=strlen(c), j=0; i>=1; i--,j++)
{
num[i] = c[j];
}
}
num[a+1] = '\0';
}
else
{
num[0] = c[0];
for( i=strlen(c)-1, j=1; i>=1; i--,j++)
{
num[i] = c[j];
}
num[a] = '\0';
}
cout<<"BigNum Constructor run"<<endl;
}
BigNum::BigNum( const BigNum &p )
{
int i=0;
if(p.num)
{
while( p.num[i] != '\0' )
{
num[i] = p.num[i];
i++;
}
num[i] = '\0';
}
cout<<"BigNum CopyConstructor run"<<endl;
}
void BigNum::setNum( char c[N] )
{
int i,j,a = strlen(c);
if( c[0] != '-')
{
num[0] = '+';
if( c )
{
for( i=strlen(c), j=0; i>=1; i--,j++)
{
num[i] = c[j];
}
}
num[a+1] = '\0';
}
else
{
num[0] = c[0];
for( i=strlen(c)-1, j=1; i>=1; i--,j++)
{
num[i] = c[j];
}
num[a] = '\0';
}
}
char const * BigNum::getNum(void) const
{
return num;
}
BigNum BigNum::operator + ( const BigNum &a )
{
if(num[0]=='+' && a.num[0]=='-')
{
BigNum s2(a);
s2.num[0] = '+';
return (*this) - s2;
}
if(num[0]=='-' && a.num[0]=='+')
{
BigNum s2(a);
num[0] = '+';
return s2 - (*this);
}
BigNum s;
int i;
char s2[N];
for( i=0; a.num[i]!='\0'; i++)
{
s2[i] = a.num[i];
}
s2[i] = '\0';
int len1 = strlen(num);
int len2 = strlen(s2);
int Max=0;
if( len1 > len2)
{
Max = len1;
num[len1] = '0';
for( i=len2; i<=len1; i++)
{
s2[i] = '0';
}
}
else
{
if( len1 < len2 )
{
Max = len2;
s2[len2] = '0';
for( i=len1; i<=len2; i++)
{
num[i] = '0';
}
}
else
{
Max = len1;
s2[len2] = '0';
num[len1] = '0';
}
}
if( (num[0]=='+' && s2[0]=='+') || (num[0]=='-' && s2[0]=='-') )
{
for( i=1; i<=Max; i++)
{
int c = ( (num[i]-'0') + (s2[i]-'0') );
if( c>= 10 )
{
c -= 10;
s.num[i] = char( c +'0');
s2[i+1]++;
}
else
{
s.num[i] = char( c + '0');
}
}
s.num[i] = '\0';
if(num[0]=='+' && s2[0]=='+')
{
s.num[0] = '+';
}
if(num[0]=='-' && s2[0]=='-' )
{
s.num[0] = '-';
}
}
return s;
}
BigNum BigNum::operator - ( BigNum &b )
{
if(num[0]=='+' && b.num[0]=='-')
{
BigNum s2(b);
s2.num[0] = '+';
return (*this) + s2;
}
if(num[0]=='-' && b.num[0]=='+')
{
BigNum s2(b);
s2.num[0] = '-';
return (*this) + s2;
}
BigNum s;
int i;
char s2[N];
for( i=0; b.num[i]!='\0'; i++)
{
s2[i] = b.num[i];
}
s2[i] = '\0';
int len1 = strlen(num);
int len2 = strlen(s2);
int Max=0;
if( len1 > len2)
{
Max = len1;
num[len1] = '0';
for( i=len2; i<=len1; i++)
{
s2[i] = '0';
}
}
else
{
if( len1 < len2 )
{
Max = len2;
s2[len2] = '0';
for( i=len1; i<=len2; i++)
{
num[i] = '0';
}
}
else
{
Max = len1;
s2[len2] = '0';
num[len1] = '0';
}
}
if( (num[0]=='+' && s2[0]=='+') || (num[0]=='-' && s2[0]=='-') )
{
if(num[0]=='-' && s2[0]=='-')
{
s2[0] = '+';
num[0] = '+';
for( i=0; num[i]!='\0'; i++ )
{
char ch;
ch = num[i];
num[i] = s2[i];
s2[i] = ch;
}
}
char s1[N];
char s3[N];
int j;
for( i=Max,j=0; i>0; j++,i--)
{
s1[j] = num[i];
}
s1[j] = '\0';
for( i=Max,j=0; i>0; j++,i--)
{
s3[j] = s2[i];
}
s3[j] = '\0';
if( strcmp(s1,s3)>0 )
{
s.num[0] = '+';
for( i=1; i<=Max; i++)
{
int c = ( (num[i]-'0') - (s2[i]-'0'));
if( c<0 )
{
c+=10;
s.num[i] = char( c + '0');
num[i+1]--;
}
else
{
s.num[i] = char( c + '0');
}
}
s.num[i] = '\0';
}
else
{
if( strcmp(s1,s3)<0 )
{
s.num[0] = '-';
for( i=1; i<=Max; i++)
{
int c = ( (s2[i]-'0') - (num[i]-'0'));
if( c<0 )
{
c+=10;
s.num[i] = char( c + '0');
s2[i+1]--;
}
else
{
s.num[i] = char( c + '0');
}
}
s.num[i] = '\0';
}
else
{
s.num[0] = '+';
s.num[1] = '0';
s.num[2] = '\0';
}
}
}
return s;
}
void BigNum::show() const
{
char ch[N] = "+0";
char c[N] = "+00";
//cout<<num<<endl;
if( strcmp(ch,num) == 0 || strcmp(c,num) == 0 )
{
cout<<"BigNum("<<ch<<")"<<endl;
}
else
{
cout<<"BigNum("<<num[0];
int i;
int flag;
for( i=strlen(num)-1; i>=0; i--)
{
if(num[i]!='0')
{
flag = i;
break;
}
}
for( i=flag; i>=1; i--)
{
cout<<num[i];
}
cout<<")"<<endl;
}
}