Cod sursa(job #2180355)
Utilizator | Data | 20 martie 2018 20:15:47 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.5 kb |
#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bool c[2000001];
int n,i,j,nr;
void ciur()
{
for(i=2; i<=n; i++)c[i]=1;
for(i=2; i<=n; i++)
{
if(c[i]==1)///i e prim=>multiplii pana la n vor fi zero
for(j=2; j*i<=n; j++)
c[i*j]=0;
}
}
int main()
{
fin>>n;
ciur();
for(i=1; i<=n; i++)
{
if(c[i]==1)nr++;
}
fout<<nr;
return 0;
}