public void FastPowTest()
{
Mint m = 2;
var x = Mint.Pow(m, 4);
Assert.AreEqual(16, x);
}
/// <summary>
/// nが大きくてkが小さいときに使える。
/// (n <= 1e9, k <= 1e7)
/// </summary>
/// <param name="n"></param>
/// <param name="k"></param>
/// <returns></returns>
public static Mint nCkForBigNSmallK(long n, long k)
{
Mint x = 1;
Mint y = 1;
for (int i = 0; i < k; i++)
{
x *= n - i;
y *= i + 1;
}
return(x / y);
}
private static void Init()
{
mFactorial = new Mint[SIZE];
mFactrialInverse = new Mint[SIZE];
mInverse = new Mint[SIZE];
mFactorial[0] = mFactorial[1] = 1;
mFactrialInverse[0] = mFactrialInverse[1] = 1;
mInverse[1] = 1;
for (int i = 2; i < SIZE; i++)
{
mFactorial[i] = mFactorial[i - 1] * i;
mInverse[i] = -1 * mInverse[Mint.MOD % i] * (Mint.MOD / i);
mFactrialInverse[i] = mFactrialInverse[i - 1] * mInverse[i];
}
}