C++ 大数运算模板

该模板可以算加，减，乘，除基本运算，其中加法只能是大数减小数。

 

 

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <algorithm>
using namespace std;

const int maxn = 1000;

struct bign
{
	int len;
	int s[maxn];

	bign()
	{
		memset( s, 0, sizeof( s ) );
		len = 1;
	}

	bign operator = ( const char * num )
	{
		len = strlen( num );
		for( int i = 0; i < len; i++ )
		{
			s[i] = num[len-1-i] - '0';
		}
		return *this;
	}

	bign operator = ( int num )
	{
		char s[maxn];
		sprintf( s, "%d", num );
		*this = s;
		return *this;
	}

	bign( int num ) 
	{
		*this = num;
	}

	bign( const char * num )
	{
		*this = num;
	}

	string str() const
	{
		string res = "";
		for( int i = 0; i < len; i++ )
			res = (char)(s[i] + '0') + res;
		if( res == "" )
			res = "0";
		return res;
	}

	/***************************************************************************************
	运算符重载: +, +=, -, -=, *, *=, /, /=, %, %=, <, <=, >, >=, !=, ==
	***************************************************************************************/
	bign operator + ( const bign& b ) const
	{
		bign c;
		c.len = 0;
		for( int i = 0, g = 0; g || i < max( len, b.len ); i++ )
		{
			int x = g;
			if( i < len ) x += s[i];
			if( i < b.len ) x += b.s[i];
			c.s[c.len++] = x % 10;
			g = x / 10;
		}
		return c;
	}

	bign operator += ( const bign& b )
	{
		*this = *this + b;
		return *this;
	}

	bign operator - ( const bign& b ) const
	{
		bign c;  
		c.len = 0;  

		for(int i = 0, g = 0; i < len; i++)  
		{  
			int x = s[i] - g;  
			if(i < b.len) x -= b.s[i];  
			if(x >= 0) g = 0;  
			else  
			{  
				g = 1;  
				x += 10;  
			}  
			c.s[c.len++] = x;  
		}  
		int n = c.len;
		for( int i = n-1; i >= 1; i-- )
			if( c.s[i] == 0 )
				c.len--;
		return c; 
	}

	bign operator -= (const bign &b)  
	{  
		*this = *this - b;  
		return *this;  
	}

	bign operator * ( const bign& b ) const
	{
		bign c;  
		c.len = len + b.len;  
		for(int i = 0; i < len; i++)  
		{  
			for(int j = 0; j < b.len; j++)  
			{  
				c.s[i+j] += s[i] * b.s[j];  
			}  
		}  
		for(int i = 0; i < c.len; i++)  
		{  
			c.s[i+1] += c.s[i]/10;  
			c.s[i] %= 10;  
		} 
		int n = c.len;
		for( int i = n-1; i >= 1; i-- )
			if( c.s[i] == 0 )
				c.len--;
		return c;
	}

	bign operator *= (const bign &b)  
	{  
		*this = *this * b;  
		return *this;  
	} 

	bign operator / (const bign &b)  
	{  
		bign c, f = 0;  
		for(int i = len-1; i >= 0; i--)  
		{  
			f = f*10;  
			f.s[0] = s[i];  
			while(f >= b)  
			{  
				f -= b;  
				c.s[i]++;  
			}  
		}  
		c.len = len;   
		int n = c.len;
		for( int i = n-1; i >= 1; i-- )
			if( c.s[i] == 0 )
				c.len--;
		return c;  
	}  

	bign operator /= (const bign &b)  
	{  
		*this  = *this / b;  
		return *this;  
	}  

	bign operator % (const bign &b)  
	{  
		bign r = *this / b;  
		r = *this - r*b;  
		return r;  
	}  
	bign operator %= (const bign &b)  
	{  
		*this = *this % b;  
		return *this;  
	}  

	bool operator < ( const bign& b ) const
	{
		if( len != b.len ) return len < b.len;

		for( int i = len-1; i >= 0; i-- )
		{
			if( s[i] != b.s[i] )
				return s[i] < b.s[i];
		}
		return false;
	}

	bool operator <= ( const bign& b ) const
	{
		return *this < b || *this == b;
	}

	bool operator > ( const bign& b ) const
	{
		if( len != b.len ) return len > b.len;

		for( int i = len-1; i >= 0; i-- )
		{
			if( s[i] != b.s[i] )
				return s[i] > b.s[i];
		}
		return false;
	}

	bool operator >= ( const bign& b ) const
	{
		return *this > b || *this == b;
	}

	bool operator != ( const bign& b ) const
	{
		return !(*this == b);
	}

	bool operator == ( const bign& b ) const
	{
		return !(*this > b) && !(*this < b);
	}


};


istream& operator >> ( istream &in, bign& x )
{
	string s;
	in >> s;
	x = s.c_str();
	return in;
}

ostream& operator << ( ostream &out, const bign& x )
{
	out << x.str();
	return out;
}

int main()
{
	bign a, b, c, d, e, f, g;
	while(cin>>a>>b)
	{
		c = a+b;
		d = a-b;
		e = a*b;
		f = a/b;
		g = a%b;
		cout<<"a+b"<<"="<<c<<endl; // a += b
		cout<<"a-b"<<"="<<d<<endl; // a -= b;
		cout<<"a*b"<<"="<<e<<endl; // a *= b;
		cout<<"a/b"<<"="<<f<<endl; // a /= b;
		cout<<"a%b"<<"="<<g<<endl; // a %= b;
		if(a != b) printf("YES\n");
		else printf("NO\n");
	}
	return 0;
}