大数运算

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
class BigNum;
istream& operator>>(istream&,BigNum&);
ostream& operator<<(istream&,BigNum&);
#define MAXN 9999
#define MAXSIZE 20000
#define DLEN 4

class BigNum
{
public:
	int a[MAXSIZE];
	int len;
public:
	BigNum()
	{
		len = 1;
		memset(a,sizeof(a));
	}
	BigNum(const int);
	BigNum(const char*);
	BigNum(const BigNum &);
	BigNum &operator=(const BigNum &);
	friend istream& operator>>(istream&,BigNum&);
	friend ostream& operator<<(ostream&,BigNum&);
	BigNum operator+(const BigNum &) const;
	BigNum operator-(const BigNum &) const;
	BigNum operator*(const BigNum &) const;
	BigNum operator/(const int &) const;
	BigNum operator^(const int &) const;
    int operator%(const int &) const;
    bool operator>(const BigNum &T) const;
	bool operator==(const BigNum &T) const;
	bool operator==(const int&) const;
	bool operator>(const int &t) const;
};

istream& operator>>(istream &in,BigNum &b)
{
	char ch[MAXSIZE*4];
	int i=-1;
	memset(b.a,sizeof(b.a));
	in>>ch;
	int l=strlen(ch);
	int count=0,sum=0;
	for( i=l-1; i>=0; )
	{
		sum = 0;
		int t = 1;
		for( int j=0; j<4&&i>=0; j++,i--,t*=10)
		{
			sum+=(ch[i]-'0')*t;
		}
		b.a[count]=sum;
		count++;
	}
	b.len = count++;
	return in;
}

ostream& operator<<(ostream& out,BigNum &b)
{
	int i;
	cout<<b.a[b.len-1];
	for( i=b.len-2; i>=0; i--)
	{
		cout.width(DLEN);
		cout.fill('0');
		cout<<b.a[i];
	}
	return out;
}

BigNum::BigNum(const int b)
{
	int c,d = b;
	len = 0;
	memset(a,sizeof(a));
	while( d > MAXN)
	{
		c=d-(d/(MAXN+1))*(MAXN+1);
		d=d/(MAXN+1);
		a[len++]=c;
	}
	a[len++] = d;
}

BigNum::BigNum( const char *s)
{
    int t,k,index,l;
	memset(a,sizeof(a));
	l=strlen(s);
	len=l/DLEN;
	if(l%DLEN) len++;
	index = 0;
	for( int i=l-1; i>=0; i-=DLEN)
	{
		t=0;
		k=i-DLEN+1;
		if(k<0)
		{
		   k=0;
		}
		for( int j=k; j<=i; j++)
		{
			t=t*10+s[j]-'0';
		}
		a[index++]=t;
	}
}

BigNum::BigNum(const BigNum &T):len(T.len)
{
	int i;
	memset(a,sizeof(a));
	for( i=0; i<len; i++)
		a[i] = T.a[i];
}
//大数与大数的赋值
BigNum &BigNum::operator=( const BigNum &n)
{
    len = n.len;
	memset(a,sizeof(a));
	for(int i=0; i<len; i++)
		a[i] = n.a[i];
	return *this;
}
//大数与大数的加法
BigNum BigNum::operator+(const BigNum &T) const
{
	BigNum t(*this);
	int i,big;
	big = T.len>len?T.len:len;
	for( i=0; i<big; i++)
	{
		t.a[i] +=T.a[i];
		if( t.a[i]>MAXN )
		{
			t.a[i+1]++;
			t.a[i]-=MAXN+1;
		}
	}
	if( t.a[big] != 0)
	{ 
		t.len = big + 1;
	}
	else
	{
		t.len = big;
	}
	return t;
}

//大数与大数的减法
BigNum BigNum::operator-(const BigNum &T) const
{
	int i,j,big;
	bool flag;
	BigNum t1,t2;
	if(*this>T)
	{
      t1=*this;
	  t2=T;
	  flag=0;
	}
	else
	{
       t1=T;
	   t2=*this;
	   flag=1;
	}
	big=t1.len;
	for(i=0; i<big; i++)
	{
		if(t1.a[i]<t2.a[i])
		{
		  j=i+1;
		  while( t1.a[j] == 0) j++;
		  t1.a[j]--;    //修改过
		  while(j>i) t1.a[j--]+=MAXN;
		  t1.a[i]+=MAXN+1-t2.a[i];
		}
		else
		  t1.a[i]-=t2.a[i];
	}

	t1.len = big;
    while(t1.a[len-1]==0&&t1.len>1)
	{
		t1.len--;
		big--;
	}
	if(flag)
		t1.a[big-1]=0-t1.a[big-1];
	return t1;

}
//大数与大数的乘法
BigNum BigNum::operator*( const BigNum &T) const
{
	BigNum ret;
	int i,up;
	int temp,temp1;
	for( i=0; i<len; i++)
	{
		up = 0;
		for( j=0; j<T.len; j++)
		{
            temp = a[i]*T.a[j]+ret.a[i+j]+up;
			if(temp>MAXN)
			{
                temp1 = temp - temp/(MAXN+1)*(MAXN+1);
				up=temp/(MAXN+1);
				ret.a[i+j]=temp1;
			}
			else
			{
				up=0;
				ret.a[i+j] = temp;
			}
		}
		if( up != 0 )
		{
			ret.a[i+j] = up;
		}
 
	}
	ret.len = i+j;
	while( ret.a[ret.len-1]==0&&ret.len>1)
	{
		ret.len--;
	}
	return ret;
}
//大数与int的除法
BigNum BigNum::operator/( const int &b) const
{
	BigNum ret;
	int i,down=0;
	for( i=len-1; i>=0; i--)
	{
		ret.a[i] = (a[i]+down*(MAXN+1))/b;
		down = a[i] +down*(MAXN+1)-ret.a[i]*b;
	}
	ret.len=len;
	while(ret.a[ret.len-1]==0&&ret.len>1) ret.len--;
	return ret;
}
//大数与int的取余
int BigNum::operator%(const int &b) const
{
    int i,d=0;
	for( i=len-1; i>=0; i--)
	{
		d=((d*(MAXN+1))%b+a[i])%b;
	}
	return b;
}
//大数幂
BigNum BigNum::operator^(const int & n) const
{    
	BigNum t,ret(1);    
	int i;    
	if(n<0)
		exit(-1);    
	if(n==0) 
		return 1;    
	if(n==1)
		return *this;    
	int m=n;    
	while(m>1)    
	{        
		t=*this;        
		for( i=1;i<<1<=m;i<<=1)
		{            
			t=t*t;        
		}      
		m-=i;       
		ret=ret*t;        
		if(m==1)ret=ret*(*this);    
	}    
	return ret;
}
//大数大小判断
bool BigNum::operator>(const BigNum & T) const
{    
	int ln;    
	if(len > T.len) 
		return true;    
	else if(len == T.len)    
	{        
		ln = len - 1;        
		while(a[ln] == T.a[ln] && ln >= 0) 
			ln--;        
		if(ln >= 0 && a[ln] > T.a[ln]) 
			return true;        
		else return false;    
	}    
	else 
		return false;
}
//大数相等判断
bool BigNum::operator==(const BigNum & T) const
{    
	int ln;   
	if(len != T.len) 
		return false;    
	else    
	{        
		ln = len - 1;        
		while(a[ln] == T.a[ln] && ln-- );        
		if(ln < 0) 
			return true;       
		else 
			return false;    
	}
}
 //大数与int 大小判断
bool BigNum::operator >(const int & t) const
{    
	BigNum b(t);   
	return *this>b;
}
//大数 与int相等判断
bool BigNum::operator==(const int & t) const
{    
	BigNum b(t);    
	return *this==b;
}
int main()
{   
    BigNum a,b;
	cin>>a;
	cin>>b;
	cout<<a+b;
	return 0;
}