Cod sursa(job #277536)
Utilizator | Stefan stefys | Data | 11 martie 2009 19:39:08 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.4 kb |
#include <fstream>
#include <iostream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
const unsigned int MAXN = 2000001;
char neprim[MAXN];
int main ()
{
unsigned int N;
in >> N;
in.close();
unsigned int i,j,nrprime=1;
for (i=3; i<=N; i+=2) {
if (!neprim[i]) {
++nrprime;
for (j=i+i; j<=N; j+=i) neprim[j]=1;
}
}
out<<nrprime<<'\n';
out.close();
return 0;
}