#### Binomial Calculate

```/**
* @file
* @brief Program to calculate [Binomial
* coefficients](https://en.wikipedia.org/wiki/Binomial_coefficient)
*
* @author [astronmax](https://github.com/astronmax)
*/

#include <cassert>   /// for assert
#include <cstdint>   /// for int32_t type
#include <cstdlib>   /// for atoi
#include <iostream>  /// for IO operations

/**
* @namespace math
* @brief Mathematical algorithms
*/
namespace math {
/**
* @namespace binomial
* @brief Functions for [Binomial
* coefficients](https://en.wikipedia.org/wiki/Binomial_coefficient)
* implementation
*/
namespace binomial {
/**
* @brief Function to calculate binomial coefficients
* @param n first value
* @param k second value
* @return binomial coefficient for n and k
*/
size_t calculate(int32_t n, int32_t k) {
// basic cases
if (k > (n / 2))
k = n - k;
if (k == 1)
return n;
if (k == 0)
return 1;

size_t result = 1;
for (int32_t i = 1; i <= k; ++i) {
result *= n - k + i;
result /= i;
}

return result;
}
}  // namespace binomial
}  // namespace math

/**
* @brief Test implementations
* @returns void
*/
static void tests() {
// tests for calculate function
assert(math::binomial::calculate(1, 1) == 1);
assert(math::binomial::calculate(57, 57) == 1);
assert(math::binomial::calculate(6, 3) == 20);
assert(math::binomial::calculate(10, 5) == 252);
assert(math::binomial::calculate(20, 10) == 184756);
assert(math::binomial::calculate(30, 15) == 155117520);
assert(math::binomial::calculate(40, 20) == 137846528820);
assert(math::binomial::calculate(50, 25) == 126410606437752);
assert(math::binomial::calculate(60, 30) == 118264581564861424);
assert(math::binomial::calculate(62, 31) == 465428353255261088);

std::cout << "[+] Binomial coefficients calculate test completed"
<< std::endl;
}

/**
* @brief Main function
* @param argc commandline argument count
* @param argv commandline array of arguments
* @returns 0 on exit
*/
int main(int argc, const char* argv[]) {
tests();  // run self-test implementations

if (argc < 3) {
std::cout << "Usage ./binomial_calculate {n} {k}" << std::endl;
return 0;
}

int32_t n = atoi(argv[1]);
int32_t k = atoi(argv[2]);

std::cout << math::binomial::calculate(n, k) << std::endl;
return 0;
}
```