Cod sursa(job #1200748)

Utilizator romykPrehari Romica romyk Data 23 iunie 2014 14:51:27
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.31 kb
Raporteaza aceasta sursa 
#include<fstream>
#include<bitset>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
const int Nmax=2000001;
int n,nr=1,i,j;
bitset <Nmax> a;
int main()
{	f>>n;
	for(i=2;i*i<=n;i++)
		if(!a[i])
			for(j=i*i;j<=n;j+=i) a[j]=1;
	for(i=3;i<=n;i+=2)
		nr+=!a[i];
	g<<nr<<"\n";
	g.close();
	return 0;
}