Sexy primes: Difference between revisions
m
Put Sieve of Eratosthenes implementation in separate header file
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m (Put Sieve of Eratosthenes implementation in separate header file) |
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</pre>
=={{header|C++}}==
<lang cpp>#include <iostream>
#include <iostream>▼
#include <vector>
#include "sieve_of_eratosthenes.h"
int main()
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// Use Sieve of Eratosthenes to find prime numbers up to max
for (int p = 2; p * p < array_size; ++p)▼
{▼
if (isprime[p])▼
{▼
for (int i = p * p; i < array_size; i += p)▼
isprime[i] = false;▼
}▼
}▼
vector<int> group_count(max_group_size);
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for (int p = 2; p < max; )
{
if (!
{
// if p + diff and p - diff aren't prime then p can't be sexy
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{
int next_p = p + i * diff;
if (next_p >= max || !
break;
++group_size;
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// skip to next prime number
++p;
while (p < max && !
++p;
}
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return 0;
}</lang>▼
Contents of sieve_of_eratosthenes.h:
<lang cpp>#ifndef SIEVE_OF_ERATOSTHENES_H
#define SIEVE_OF_ERATOSTHENES_H
class sieve_of_eratosthenes
{
public:
explicit sieve_of_eratosthenes(size_t);
bool is_prime(size_t) const;
private:
std::vector<bool> is_prime_;
};
inline bool sieve_of_eratosthenes::is_prime(size_t n) const
{
return is_prime_[n];
}
▲</lang>
inline sieve_of_eratosthenes::sieve_of_eratosthenes(size_t max)
: is_prime_(max, true)
{
is_prime_[0] = is_prime_[1] = false;
▲ {
▲ {
▲ }
▲ }
}
#endif</lang>
{{out}}
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