private static double PValueForSmallN(int n, int m, double u)
{
int q = (int)Math.Floor(u + 1e-9);
int nm = Math.Max(n, m);
var w = new long[nm + 1, nm + 1, q + 1];
for (int i = 0; i <= nm; i++)
{
for (int j = 0; j <= nm; j++)
{
for (int k = 0; k <= q; k++)
{
if (i == 0 || j == 0 || k == 0)
{
w[i, j, k] = k == 0 ? 1 : 0;
}
else if (k > i * j)
{
w[i, j, k] = 0;
}
else if (i > j)
{
w[i, j, k] = w[j, i, k];
}
else if (j > 0 && k < j)
{
w[i, j, k] = w[i, k, k];
}
else
{
w[i, j, k] = w[i - 1, j, k - j] + w[i, j - 1, k];
}
}
}
}
long denominator = BinomialCoefficientHelper.GetBinomialCoefficient(n + m, m);
long p = 0;
if (q <= n * m / 2)
{
for (int i = 0; i <= q; i++)
{
p += w[n, m, i];
}
}
else
{
q = n * m - q;
for (int i = 0; i < q; i++)
{
p += w[n, m, i];
}
p = denominator - p;
}
return(p * 1.0 / denominator);
}
public double Pmf(int k)
{
if (k < 0 || k > N)
{
return(0);
}
return(Math.Exp(
BinomialCoefficientHelper.GetLogBinomialCoefficient(N, k) +
k * Math.Log(P) +
(N - k) * Math.Log(1 - P)
));
}
public void BinomialCoefficientTest(int n, int k, long expected)
{
long actual = BinomialCoefficientHelper.GetBinomialCoefficient(n, k);
Assert.Equal(expected, actual);
}
