1  #include <vector>
  2  #include <iostream>
  3  
  4  using namespace std;
  5  
  6  int main()
  7  {
  8     // Create the sieve, initially true
  9     const int sievesize = 100;
 10     vector<bool> sieve(sievesize, true);
 11     // Now search for positions with true
 12     for (int i = 2; i * i < sievesize; i++)
 13        if (sieve[i])
 14           // Strike out multiples
 15           for (int j = i + i; j < sievesize; j += i)
 16              sieve[j] = false;
 17     // Output values that remain set
 18     for (int i = 2; i < sievesize; i++)
 19        if (sieve[i])
 20           cout << i << " is prime\n";
 21     return 0;
 22  }