Cod sursa(job #302031)
Utilizator | Alexandra alex@ndra | Data | 8 aprilie 2009 16:55:52 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.61 kb |
#include<fstream>
using namespace std;
long prim[200001];
long n, i, j, nr=0;
int main()
{
ifstream f("ciur.in");
f>>n;
f.close();
prim[1]=0;
for(i=2;i<=n;i++)
prim[i]=1;
for(i=2;i<=n;i++)
if(prim[i]==1)
for(j=i+i;j<=n;j=j+i)
prim[j]=0;
for(i=1;i<=n;i++)
if(prim[i]) nr++;
ofstream g("ciur.out");
g<<nr;
g.close();
return 0;
}