docs: public static int nChooseK(int n, int k) {
      k = Math.min(k, n - k);
      if (k == 0) {
        return 1;
      }
      int accum = n;
      for (int i = 1; i < k; i++) {
        accum *= (n - i);
        accum /= i;
      }
      return accum / k;
    }