static bigInt GCD(bigInt a, bigInt b)
{
if (a.equalToZero() || b.equalToZero())
{
return(a + b);
}
string bits = "1";
bigInt gcd = new bigInt(bits);
while (a._bits[a._length - 1] == '0' && b._bits[b._length - 1] == '0')
{
a = a >> 1;
b = b >> 1;
gcd = gcd << 1;
}
while (!a.equalToZero())
{
while (a._bits[a._length - 1] == '0')
{
a = a >> 1;
}
while (b._bits[b._length - 1] == '0')
{
b = b >> 1;
}
bigInt t;
if (a > b)
{
t = a - b;
}
else
{
t = b - a;
}
t = t >> 1;
if (a > b || a == b)
{
a = t;
}
else
{
b = t;
}
}
if (a._length > b._length)
{
gcd = gcd >> b._length;
}
else
{
gcd = gcd >> a._length;
}
gcd = bigInt.standardize(gcd);
return(gcd);
}
static bigInt powerMod(bigInt x, bigInt p, bigInt n)
{
//Return: result = (x ^ p) % n
x = x % n;
String bits = "1";
bigInt result = new bigInt(bits);
// if (p == 0) return 1;
if (p.equalToZero())
{
return(result);
}
else
{
//Cach 1:
//bigInt a = new bigInt(x._bits);
//if (p._bits[p._length - 1] == '1') result = x;
//for (int i = 1; i < p._length; i++)
//{
// a = mulMod(a, a, n);
// if (p._bits[p._length - 1 - i] == '1') result = mulMod(result, a, n);
//}
//Cach 2
for (int i = 0; i < p._length; i++)
{
result = mulMod(result, result, n);
if (p._bits[i] == '1')
{
result = mulMod(result, x, n);
}
}
}
result = bigInt.standardize(result);
return(result);
}
