LargeNumbers(NumSign sign, IEnumerable <int> digits, int decimalPlaces)
{
Sign = sign;
Digits = new ReadOnlyCollection <int>(digits.ToList());
DecimalPlaces = decimalPlaces;
}
public static LargeNumbers Sub(LargeNumbers first, LargeNumbers second)
{
if (first.Sign == NumSign.Negative && second.Sign == NumSign.Positive)
{
LargeNumbers positiveFirst = new LargeNumbers(NumSign.Positive, first.Digits, first.DecimalPlaces);
LargeNumbers sum = Add(positiveFirst, second);
return(new LargeNumbers(NumSign.Negative, sum.Digits, sum.DecimalPlaces));
}
else if (first.Sign == NumSign.Positive && second.Sign == NumSign.Negative)
{
LargeNumbers positiveSecond = new LargeNumbers(NumSign.Positive, second.Digits, second.DecimalPlaces);
return(Add(first, positiveSecond));
}
else
{
List <int> digits1 = first.Digits.ToList();
List <int> digits2 = second.Digits.ToList();
List <int> resultDigits = new List <int>();
NumSign resultSign = new NumSign();
if ((digits1.Count - first.DecimalPlaces) < (digits2.Count - second.DecimalPlaces))
{
if (first.Sign == NumSign.Positive && second.Sign == NumSign.Positive)
{
LargeNumbers sum = Sub(second, first);
return(new LargeNumbers(NumSign.Negative, sum.Digits, sum.DecimalPlaces));
}
else if (first.Sign == NumSign.Negative && second.Sign == NumSign.Negative)
{
LargeNumbers sum = Sub(second, first);
return(new LargeNumbers(NumSign.Positive, sum.Digits, sum.DecimalPlaces));
}
}
int maxDigitsBeforeDecimalPoint = Math.Max(
(digits1.Count - first.DecimalPlaces),
(digits2.Count - second.DecimalPlaces));
digits1.InsertRange(0, Enumerable.Repeat(0, maxDigitsBeforeDecimalPoint - (digits1.Count - first.DecimalPlaces)));
digits2.InsertRange(0, Enumerable.Repeat(0, maxDigitsBeforeDecimalPoint - (digits2.Count - second.DecimalPlaces)));
int maxDigitsAfterDecimalPoint = Math.Max(
first.DecimalPlaces,
second.DecimalPlaces
);
digits1.AddRange(Enumerable.Repeat(0, maxDigitsAfterDecimalPoint - first.DecimalPlaces));
digits2.AddRange(Enumerable.Repeat(0, maxDigitsAfterDecimalPoint - second.DecimalPlaces));
int carry = 0;
if (digits1[0] < digits2[0])
{
if (first.Sign == NumSign.Positive && second.Sign == NumSign.Positive)
{
LargeNumbers sum = Sub(second, first);
return(new LargeNumbers(NumSign.Negative, sum.Digits, sum.DecimalPlaces));
}
else if (first.Sign == NumSign.Negative && second.Sign == NumSign.Negative)
{
LargeNumbers sum = Sub(second, first);
return(new LargeNumbers(NumSign.Positive, sum.Digits, sum.DecimalPlaces));
}
}
else if (digits1[0] == digits2[0])
{
int i = -1;
do
{
++i;
if (i == digits1.Count - 1 && i == digits2.Count - 1 && digits1[i] == digits2[i])
{
break;
}
else if (digits1[i] < digits2[i])
{
if (first.Sign == NumSign.Positive && second.Sign == NumSign.Positive)
{
LargeNumbers sum = Sub(second, first);
return(new LargeNumbers(NumSign.Negative, sum.Digits, sum.DecimalPlaces));
}
else if (first.Sign == NumSign.Negative && second.Sign == NumSign.Negative)
{
LargeNumbers sum = Sub(second, first);
return(new LargeNumbers(NumSign.Positive, sum.Digits, sum.DecimalPlaces));
}
}
} while (digits1[i] == digits2[i] && i != digits2.Count);
}
for (int i = digits1.Count - 1; i >= 0; i--)
{
if (digits1[i] - digits2[i] - carry < 0)
{
resultDigits.Insert(0, (10 - digits2[i] + digits1[i] - carry));
carry = 1;
}
else
{
resultDigits.Insert(0, ((digits1[i] - carry) - digits2[i]));
carry = 0;
}
}
if (carry == 0)
{
resultSign = first.Sign;
}
if (carry == 1)
{
resultSign = second.Sign;
}
return(new LargeNumbers(resultSign, resultDigits, maxDigitsAfterDecimalPoint));
}
}
