Cod sursa(job #313221)
Utilizator | Muraru Costin costin22 | Data | 8 mai 2009 12:50:45 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.53 kb |
#include <stdio.h>
#include <vector>
#define N 2000200
//#define FOR(i,1,n) for(i=1;i<=n;++i)
//const int N=2000200;
using namespace std;
int main()
{
freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);
int i,j,nr,n;
scanf("%d",&n);
nr=0;
//bool c[N]={false};
vector <bool> c(N,false);
for (i=2; i*i<=n; ++i)
//FOR(i,1,n)
{
if (c[i]==false)
for (j=i*i; j<=n; j=j+i)
c[j]=true;
}
for (i=2; i<=n; ++i)
{
if (!c[i])
nr++;
}
printf("%d",nr);
return 0;
}