[Shootout-list] nsieve g++ c++ (now with vectors)

[Daniel Skiles]

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Hey all,
I followed Falk's recommendations.  The code is shorter and actually
works for argument values of greater than two, but I don't really have
any way to time it.  Please disregard my previous attempt.

Daniel

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#include <cstdlib>
#include <iostream>
#include <vector>

using namespace std;

int nsieve(int);

int main(int argc, char *argv[])
{
    int n =3D (argc =3D=3D 2) ? atoi(argv[1]) : 2;
    int m;
   =20
    m =3D (1<<n)*10000;
    cout << "Primes up to " << m << " " << nsieve(m) << endl;
   =20
    m =3D (1<<n-1)*10000;
    cout << "Primes up to " << m << " " << nsieve(m) << endl;
   =20
    m =3D (1<<n-2)*10000;
    cout << "Primes up to " << m << " " << nsieve(m) << endl;
   =20
    return EXIT_SUCCESS;
}

int nsieve(int m)
{
    vector<bool> isPrime(m, true);
    int count =3D 0;
       =20
    for(int i=3D2; i<=3Dm; i++){
        if(isPrime[i]){
            for(int k=3Di*2; k<=3Dm; k+=3Di){
                isPrime[k] =3D false;
            }
            count++;
        }
    }
    return count;
}


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