public static string Add(string a, string b)
{
var lhs = PositiveBigInteger.Parse(a);
var rhs = PositiveBigInteger.Parse(b);
var sum = PositiveBigInteger.Add(lhs, rhs);
return(sum.ToString());
}
public static PositiveBigInteger Add(PositiveBigInteger lhs, PositiveBigInteger rhs)
{
var minLength = Math.Min(lhs._bits.Length, rhs._bits.Length);
var maxLength = Math.Max(lhs._bits.Length, rhs._bits.Length);
var sumBits = new uint[maxLength];
var longerBits = maxLength == lhs._bits.Length ? lhs._bits : rhs._bits;
uint carry = 0;
for (var i = 0; i < minLength; i++)
{
var currentSum = lhs._bits[i] + rhs._bits[i] + carry;
if (currentSum >= MaxUnits)
{
sumBits[i] = currentSum - MaxUnits;
carry = 1;
}
else
{
sumBits[i] = currentSum;
carry = 0;
}
}
for (var i = minLength; i < maxLength; i++)
{
var currentSum = longerBits[i] + carry;
if (currentSum >= MaxUnits)
{
sumBits[i] = currentSum - MaxUnits;
carry = 1;
}
else
{
sumBits[i] = currentSum;
carry = 0;
}
}
if (carry == 1)
{
var oldSumBits = sumBits;
sumBits = new uint[oldSumBits.Length + 1];
for (var i = 0; i < oldSumBits.Length; i++)
{
sumBits[i] = oldSumBits[i];
}
sumBits[sumBits.Length - 1] = 1;
}
return(new PositiveBigInteger(sumBits));
}