GCD

The greatest common divisor can be calculated

* using a for-loop

* using recursion

* using the Boost library

Code in plain text can be found here.

A for-loop

Using Euclid's algorithm.

int GreatestCommonDivisor(int x, int y)

{

while (y != 0)

{

const int temp = y;

y = x % y;

x = temp;

}

return x;

}

Using Euclid's algorithm, a recursive function:

int GreatestCommonDivisor(const int x, const int y)

{

if (y==0) return x;

return GreatestCommonDivisor(y,x%y);

}

#include <boost/math/common_factor.hpp>

#include <algorithm>

#include <iterator>

#include <iostream>

int main()

{

using std::cout;

using std::endl;

cout << "The GCD and LCM of 6 and 15 are "

<< boost::math::gcd(6, 15) << " and "

<< boost::math::lcm(6, 15) << ", respectively."

<< endl;

cout << "The GCD and LCM of 8 and 9 are "

<< boost::math::static_gcd<8, 9>::value

<< " and "

<< boost::math::static_lcm<8, 9>::value

<< ", respectively." << endl;

std::cin.get();

}