Sequence of primorial primes: Difference between revisions
Added C++ solution
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=={{header|C++}}==
{{libheader|GMP}}
<lang cpp>#include <cstdint>
#include <iostream>
#include <sstream>
#include <vector>
#include <gmpxx.h>
typedef mpz_class integer;
void find_primes(std::vector<bool>& isprime, size_t limit)
{
isprime.assign(limit, true);
isprime[0] = isprime[1] = false;
for (size_t p = 2; p * p < limit; ++p)
{
if (isprime[p])
{
for (size_t i = p * p; i < limit; i += p)
isprime[i] = false;
}
}
}
bool is_prime(const integer& n)
{
return mpz_probab_prime_p(n.get_mpz_t(), 25);
}
int main()
{
const size_t max_prime = 4000;
const size_t max = 20;
std::vector<bool> isprime;
find_primes(isprime, max_prime);
integer primorial = 1;
for (size_t p = 0, count = 0, index = 0; p < max_prime && count < max; ++p)
{
if (!isprime[p])
continue;
primorial *= p;
++index;
if (is_prime(primorial - 1) || is_prime(primorial + 1))
{
if (count > 0)
std::cout << ' ';
std::cout << index;
++count;
}
}
std::cout << '\n';
return 0;
}</lang>
{{out}}
<pre>
1 2 3 4 5 6 11 13 24 66 68 75 167 171 172 287 310 352 384 457
</pre>
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