Cod sursa(job #1013972)
Utilizator | Data | 21 octombrie 2013 22:35:22 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.36 kb |
#include<fstream>
#define maxn 2000005
using namespace std;
ifstream fi("ciur.in");
ofstream fo("ciur.out");
bool a[maxn];
int i,j,n,k;
int main(){
fi>>n; k=0;
for(i=2;i<=n;i++) a[i]=true;
for(i=2;i<=n;i++)
if (a[i]) {k++; for(j=2*i;j<=n;j+=i) a[j]=false;}
fo<<k;
fi.close();
fo.close();
return 0;
}