Cod sursa(job #574304)
Utilizator | FMI Cernat Catalin Stefan cernat.catallin | Data | 7 aprilie 2011 00:53:46 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 0 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.45 kb |
#include <fstream>
#include <math.h>
using namespace std;
int main()
{
ofstream g ("ciur.out");
ifstream f ("ciur.in");
char p[1000050];
long n,nr=1;
float rad;
f>>n;
f.close();
for(int i=2;i<=n;i++) p[i]=0;
rad=sqrt(n);
for(int i=1;i<=rad;i++) //2*i+1
{
if(p[i]==0)
{ nr++;
for(int j=2*i*i+2*i;2*j+1<=n;j+=2*i+1) p[j]=1;
}
}
g<<nr;
g.close();
}