Fortunate numbers: Difference between revisions
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=={{header|C++}}==
<syntaxhighlight lang="c++">
#include <algorithm>
#include <cstdint>
#include <iostream>
#include <set>
#include <vector>
std::vector<int32_t> prime_numbers(const int32_t& limit) {
const int32_t half_limit = ( limit % 2 == 0 ) ? limit / 2 : 1 + limit / 2;
std::vector<bool> composite(half_limit, false);
for ( int32_t i = 1, p = 3; i < half_limit; p += 2, ++i ) {
if ( ! composite[i] ) {
for ( int32_t a = i + p; a < half_limit; a += p ) {
composite[a] = true;
}
}
}
std::vector<int32_t> primes{2};
for ( int32_t i = 1, p = 3; i < half_limit; p += 2, ++i ) {
if ( ! composite[i] ) {
primes.push_back(p);
}
}
return primes;
}
bool contains(const std::vector<int32_t>& list, const int32_t& n) {
return std::find(list.begin(), list.end(), n) != list.end();
}
int main() {
std::vector<int32_t> primes = prime_numbers(250'000'000);
std::set<int32_t> fortunates;
int32_t primorial = 1;
int32_t index = 0;
while ( fortunates.size() < 8 ) {
primorial *= primes[index++];
int32_t candidate = 3;
while ( ! contains(primes, primorial + candidate) ) {
candidate += 2;
}
fortunates.emplace(candidate);
}
std::cout << "The first 8 distinct fortunate numbers are:" << std::endl;
for ( const int32_t& fortunate : fortunates ) {
std::cout << fortunate << " ";
}
}
<syntaxhighlight>
<pre>
The first 8 distinct fortunate numbers are:
3 5 7 13 17 19 23 37
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