Cod sursa(job #2050758)
Utilizator | Alexandrescu Diana AlexDiana | Data | 28 octombrie 2017 11:16:28 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.56 kb |
#include <bitset>
#include <fstream>
using namespace std;
const int N=2000000;
bitset<N+1>p;
int main()
{
int n;
ifstream in("ciur.in");
ofstream out("ciur.out");
in>>n;
p.set();
for(int i=2;i*i<=n;i++)
{
if(p[i])
{
for(int j=i*i;j<=n;j+=i)
{
p[j]=false;
}
}
}
in.close();
int nr=0;
for(int i=2;i<=n;i++)
{
if(p[i])
{
nr++;
}
}
out<<nr;
out.close();
return 0;
}