Ormiston triples: Difference between revisions
Added C++ solution
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* [[Ormiston pairs]]
<br>
=={{header|C++}}==
{{libheader|Primesieve}}
<syntaxhighlight lang="cpp">#include <array>
#include <iostream>
#include <primesieve.hpp>
class ormiston_triple_generator {
public:
ormiston_triple_generator() {
for (int i = 0; i < 2; ++i) {
primes_[i] = pi_.next_prime();
digits_[i] = get_digits(primes_[i]);
}
}
std::array<uint64_t, 3> next_triple() {
for (;;) {
uint64_t prime = pi_.next_prime();
auto digits = get_digits(prime);
bool is_triple = digits == digits_[0] && digits == digits_[1];
uint64_t prime0 = primes_[0];
primes_[0] = primes_[1];
primes_[1] = prime;
digits_[0] = digits_[1];
digits_[1] = digits;
if (is_triple)
return {prime0, primes_[0], primes_[1]};
}
}
private:
static std::array<int, 10> get_digits(uint64_t n) {
std::array<int, 10> result = {};
for (; n > 0; n /= 10)
++result[n % 10];
return result;
}
primesieve::iterator pi_;
std::array<uint64_t, 2> primes_;
std::array<std::array<int, 10>, 2> digits_;
};
int main() {
ormiston_triple_generator generator;
int count = 0;
std::cout << "Smallest members of first 25 Ormiston triples:\n";
for (; count < 25; ++count) {
auto primes = generator.next_triple();
std::cout << primes[0] << ((count + 1) % 5 == 0 ? '\n' : ' ');
}
std::cout << '\n';
for (uint64_t limit = 1000000000; limit <= 10000000000; ++count) {
auto primes = generator.next_triple();
if (primes[2] > limit) {
std::cout << "Number of Ormiston triples < " << limit << ": "
<< count << '\n';
limit *= 10;
}
}
}</syntaxhighlight>
{{out}}
<pre>
Smallest members of first 25 Ormiston triples:
11117123 12980783 14964017 32638213 32964341
33539783 35868013 44058013 46103237 48015013
50324237 52402783 58005239 60601237 61395239
74699789 76012879 78163123 80905879 81966341
82324237 82523017 83279783 86050781 92514341
Number of Ormiston triples < 1000000000: 368
Number of Ormiston triples < 10000000000: 4925
</pre>
=={{header|Go}}==
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