net.jqwik.engine.support.MathSupport Maven / Gradle / Ivy
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package net.jqwik.engine.support;
public class MathSupport {
public static long factorial(long number) {
if (number > 20) {
throw new ArithmeticException("MathSupport.factorial() only works till 20");
}
long result = 1;
for (long factor = 2; factor <= number; factor++) {
result *= factor;
}
return result;
}
// From https://rosettacode.org/wiki/Evaluate_binomial_coefficients#Java
// Faster than return factorial(n) / (factorial(n - k) * factorial(k));
// Max n = 70
public static long binomial(int n, int k) {
if (n > 70) {
throw new ArithmeticException("MathSupport.binomial() only works till 70");
}
if (k > n - k) {
k = n - k;
}
long b = 1;
for (int i = 1, m = n; i <= k; i++, m--) {
b = b * m / i;
}
return b;
}
}