Cod sursa(job #1814577)
Utilizator | Bogdan Pintilie bogdanpintilie19 | Data | 24 noiembrie 2016 11:16:12 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.52 kb |
#include <fstream>
using namespace std;
long long n, t[2000005];
int cnt;
void Ciur()
{
int i;
t[1]=1;
for(i=2; i<= n; i+=2)
t[i]=1;
t[2]=0;
for(i=3; i*i<=n; i++)
for(int j=i*i; j<=n; j+=2*i)
t[j]=1;
for(i=1; i<=n; i++)
if(t[i]==0) cnt++;
}
int main()
{
ifstream fin("ciur.in");
fin >> n;
fin.close();
ofstream fout("ciur.out");
Ciur();
fout<<cnt<<"\n";
fout.close();
return 0;
}