Cod sursa(job #2282473)
Utilizator | Kulcsar Noemi Noemikulcsar | Data | 13 noiembrie 2018 19:49:39 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 90 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.54 kb |
#include <fstream>
#include <iostream>
using namespace std;
int main()
{
ifstream fin("ciur.in");
ofstream fout("ciur.out");
char prim[2000005];
int i,n,k=0,j;
fin>>n;
for(i=1;i<=n;i+=2)
prim[i]=1;
prim[1]=0;
prim[2]=1;
for(i=3;i*i<=n;i=i+2)
{
if(prim[i]==1)
for(j=i*i;j<=n;j=j+2*i)
{
prim[j]=0;
}
}
for(i=1;i<=n;i++)
{
if(prim[i]==1)
k++;
}
fout<<k;
return 0;
}