schoolFactor.cpp

#include <iostream>
#include <boost/multiprecision/cpp_int.hpp>
#include <chrono>

using namespace boost::multiprecision;
using namespace std;

class stoper
{
public:
	chrono::time_point<chrono::high_resolution_clock> a, b;
	void start() { a = chrono::high_resolution_clock::now(); }
	void stop() { b = chrono::high_resolution_clock::now(); }
	double duration()
	{
		chrono::duration<double> elapsed_seconds = b - a;
		return elapsed_seconds.count();
	}
};

void factor(const cpp_int n)
{
	cpp_int x = n;
	while ((x % 2) == 0) {
		x /= 2;
		std::cout << 2 << " ";
	}
	cpp_int i, e;
	i = 3;
	e = sqrt(x);
	while (i <= e) {
		while ((x % i) == 0) {
			x /= i;
			e = sqrt(x);
			std::cout << i << " ";
		}
		i+=2;
	}
	if (x > 1)
		std::cout << x << " ";
}

int main()
{
	cpp_int a("5742507205757425072053");// 3*7*197*402529*3448409664461 
	double best = INFINITY;	
	for (int i=0; i<10; i++)
    {
        stoper st;
        st.start();
        factor(a);
        st.stop();
        best = min(best, st.duration());
    }
    printf("%f\n", best);
    return 0;
}