mirror of
https://hub.njuu.cf/TheAlgorithms/C-Plus-Plus.git
synced 2023-10-11 13:05:55 +08:00
0b890fd842
* Add program to calculate binomial coefficients
* docs: add link to github profile, change cmath to cstdlib
* correction of comments, adding math namespace
* updating DIRECTORY.md
* Adding binomial namespace, rename function and filename, correcting comments
* updating DIRECTORY.md
Co-authored-by: astronmax <astronmax@yandex.ru>
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
93 lines
2.3 KiB
C++
93 lines
2.3 KiB
C++
/**
|
|
* @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;
|
|
}
|