大数相加基于字符串

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• 大数相加基于字符串

大数相加基于字符串

/**
  * @name   Big_Number_Add
  * @brief  基于字符串的大数相加函数
  * @author Velscode 
  * @para   R[] is the string of result of A+B
  */
void Big_Number_Add( char A[], char B[], char R[] )
{
	long long int len_a = 0, len_b = 0,i,j;
	unsigned char carry_bit = 0, next_carry_bit = 0 ;
	char * p;
	
	//calculate length of A[]
	p = A;
	
	while( *p != '\0' )
	{
		p++;
		len_a++;
	}
	
	
	//calculate length of B[]
	p = B;
	
	while( *p != '\0' )
	{
		p++;
		len_b++;
	}
	
	if( len_a >= len_b )
	{
		R[len_a+1] = '\0';
		
		for( i = 0; i < len_b; i++)
		{
			R[len_a-i] =      ( (A[len_a-1-i] - '0' + B[len_b-1-i] - '0') + carry_bit ) % 10 + 48;
			next_carry_bit =  ( (A[len_a-1-i] - '0' + B[len_b-1-i] - '0') + carry_bit ) / 10;
			carry_bit = next_carry_bit;
		}
		
		for( ; i < len_a; i++)
		{
			R[len_a-i] =      ( (A[len_a-1-i] - '0') + carry_bit ) % 10 + 48;
			next_carry_bit =  ( (A[len_a-1-i] - '0') + carry_bit ) / 10 ;
			carry_bit = next_carry_bit;
		}
		
		if( carry_bit != 0 )
			R[0] = carry_bit + 48;
		else
		{
			for(i=0;i<len_a;i++)
				R[i] = R[i+1];
		
			R[i] = '\0';
		}

	}
	
	if( len_a < len_b )
	{
		R[len_b+1] = '\0';
		
		for( i = 0; i < len_a; i++)
		{
			R[len_b-i] =      ( (A[len_a-1-i] - '0' + B[len_b-1-i] - '0') + carry_bit ) % 10 + 48;
			next_carry_bit =  ( (A[len_a-1-i] - '0' + B[len_b-1-i] - '0') + carry_bit ) / 10;
			carry_bit = next_carry_bit;
		}
		
		for( ; i < len_b; i++)
		{
			R[len_b-i] =      ( (B[len_b-1-i] - '0') + carry_bit ) % 10 + 48;
			next_carry_bit =  ( (B[len_b-1-i] - '0') + carry_bit ) / 10 ;
			carry_bit = next_carry_bit;
		}
		
		if( carry_bit != 0 )
			R[0] = carry_bit + 48;
		else
		{
			for(i=0;i<len_b;i++)
				R[i] = R[i+1];
		
			R[i] = '\0';
		}

	}
		
	return ;
}