Cod sursa(job #1364714)
Utilizator | Daria Marc marcdaria | Data | 27 februarie 2015 19:53:04 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.44 kb |
#include <fstream>
#define N 200000
using namespace std;
int main()
{
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bool ciur[2000001];
long n,i,j;
for(i=2;i<=N;++i) ciur[i]=true;
fin>>n;
int cnt=0;
for(i=2;i<=n;++i)
if(ciur[i]==true){
++cnt;
for(j=i+i;j<=n;j=j+i)
ciur[j]=false;}
fout<<cnt;
fin.close();
fout.close();
return 0;
}