problem005.cpp

#include "lib/primesieve.h"

#include <cmath>
#include <iostream>

int lcmOfRange(int upper)
{
 int result = 1;
 int sqrtLimit = sqrt(upper);
 PrimeSieve sieve(upper);
 int primes = sieve.countPrimes();
 for (int i = 1; i <= primes; ++i) {
 int p = sieve.nthPrime(i);
 int x = p;
 if (p <= sqrtLimit) {
 int product = p * p;
 do {
 x = product;
 product *= p;
 } while (product <= upper);
 }
 result *= x; // x = p_i^(floor(log_p_i(upper)))
 }
 return result;
}

int main()
{
 std::cout << "Answer: " << lcmOfRange(20) << '\n';
 return 0;
}