Cod sursa(job #2180498)
Utilizator | Din Iulian Andrulian | Data | 20 martie 2018 21:58:23 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.56 kb |
#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
char c[2000001];
int n,i,j,nr;
void ciur()
{
for(i=2; i<=n; i++)c[i]=1;
for(i=2; i*i<=n; i++)
{
if(c[i]==1)///i e prim=>multiplii pana la n vor fi zero
for(j=i*i; j<=n; j=j+i)
c[j]=0;
}
}
int main()
{
fin>>n;
ciur();
for(i=1; i<=n; i++)
{
if(c[i]==1)
{
nr++;
// cout<<i<<" ";
}
}
fout<<nr;
return 0;
}