Cod sursa(job #392206)
Utilizator | Data | 6 februarie 2010 23:24:24 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.47 kb |
#include <fstream>
using namespace std;
#include <vector>
ifstream in ( "ciur.in" );
ofstream out ( "ciur.out" );
int N;
vector <bool> v ( 2000000 );
void ciur ( int N )
{
int cnt = 0;
for ( int i = 1; i <= N; ++i )
v [ i ] = true;
for ( int i = 2; i <= N; ++i )
if ( v [ i ] )
{
++cnt;
for ( int j = i + i; j <= N; j += i )
v [ j ] = false;
}
out << cnt;
}
int main ()
{
in >> N;
ciur ( N );
return 0;
}