examples/tutorial/sieve.cpp

/**************************************************************************
 *
 * sieve.cpp - Prime numbers sieve program.
 *
 * $Id: //stdlib/dev/examples/stdlib/tutorial/sieve.cpp#11 $
 *
 ***************************************************************************
 *
 * Copyright (c) 1994-2005 Quovadx,  Inc., acting through its  Rogue Wave
 * Software division. Licensed under the Apache License, Version 2.0 (the
 * "License");  you may  not use this file except  in compliance with the
 * License.    You    may   obtain   a   copy   of    the   License    at
 * http://www.apache.org/licenses/LICENSE-2.0.    Unless   required    by
 * applicable law  or agreed to  in writing,  software  distributed under
 * the License is distributed on an "AS IS" BASIS,  WITHOUT WARRANTIES OR
 * CONDITIONS OF  ANY KIND, either  express or implied.  See  the License
 * for the specific language governing permissions  and limitations under
 * the License.
 * 
 **************************************************************************/

#include <vector>
#include <iostream>

#include <examples.h>
    
int main ()
{

    std::cout << "Prime Sieve program, a test of vectors" << std::endl;

    // Create a sieve of bits, initially set to 1.
    const int sievesize = 100;
    std::vector<int, std::allocator<int> > sieve ((std::size_t)sievesize, 1);

    // At positions that are multiples of i, set value to zero.
    for (int i = 2; i * i < sievesize; i++)
        if (sieve[i])
            for (int j = i + i; j < sievesize; j += i)
                sieve[j] = 0;

    // Now output all the values that are still set.
    for (int j = 2; j < sievesize; j++)
        if (sieve[j]) 
            std::cout << j << " ";
    
    std::cout << std::endl << "End of Prime Sieve program" << std::endl;

    return 0;
}