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miller_rabin.cpp
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81 lines (70 loc) · 1.45 KB
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#include "miller_rabin.h"
#include <random>
auto MillerRabin::ModularExponentiation(int base, int exponent, const int mod) -> int
{
int result = 1;
while (exponent > 0)
{
if (exponent % 2 == 1)
{
result = (result * base) % mod;
}
exponent /= 2;
base = (base * base) % mod;
}
return result;
}
auto MillerRabin::Witness(int exponent, const int number) -> bool
{
std::random_device rd;
std::mt19937 generator(rd());
std::uniform_int_distribution distribution(2, number - 1);
const int random = distribution(generator);
int x = ModularExponentiation(random, exponent, number);
if (x == 1 || x == number - 1)
{
return true;
}
while (exponent != number - 1)
{
x = (x * x) % number;
exponent *= 2;
if (x == 1)
{
return false;
}
if (x == number - 1)
{
return true;
}
}
return false;
}
auto MillerRabin::MillerRabinPrimalityTest(const int number, const int repeats) -> bool
{
if (number < 2)
{
return false;
}
if (number == 2)
{
return true;
}
if (number % 2 == 0)
{
return false;
}
int d = number - 1;
while (d % 2 == 0)
{
d /= 2;
}
for (int i = 0; i < repeats; ++i)
{
if (!Witness(d, number))
{
return false;
}
}
return true;
}