n_choose_r.cpp File Reference

Combinations n choose r function implementation More...

#include <cassert>
#include <iostream>

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Namespaces
	math
	for std::vector

Functions
template<class T >
T	math::n_choose_r (T n, T r)
	This is the function implementation of \( \binom{n}{r} \). More...
static void	test ()
	Test implementations. More...
int	main (int argc, char *argv[])
	Main function. More...

Detailed Description

Combinations n choose r function implementation

A very basic and efficient method of calculating choosing r from n different choices. \( \binom{n}{r} = \frac{n!}{r! (n-r)!} \)

Author

Tajmeet Singh

Function Documentation

main()

int main	(	int	argc,
		char *	argv[]
	)

Main function.

Parameters

argc	commandline argument count (ignored)
argv	commandline array of arguments (ignored)

Returns

0 on exit

                                 {
    test();  // executing tests
    return 0;
}

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test()

static void test ( )

static

Test implementations.

Returns

void

                   {
    // First test on 5 choose 2
    uint8_t t = math::n_choose_r(5, 2);
    assert(((void)"10 is the answer but function says otherwise.\n", t == 10));
    std::cout << "First test passes." << std::endl;
    // Second test on 5 choose 3
    t = math::n_choose_r(5, 3);
    assert(
        ((void)"10 is the answer but the function says otherwise.\n", t == 10));
    std::cout << "Second test passes." << std::endl;
    // Third test on 3 choose 2
    t = math::n_choose_r(3, 2);
    assert(
        ((void)"3 is the answer but the function says otherwise.\n", t == 3));
    std::cout << "Third test passes." << std::endl;
    // Fourth test on 10 choose 4
    t = math::n_choose_r(10, 4);
    assert(((void)"210 is the answer but the function says otherwise.\n",
            t == 210));
    std::cout << "Fourth test passes." << std::endl;
}

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