Cod sursa(job #811291)
Utilizator | Claudiu Ion cldme | Data | 11 noiembrie 2012 20:37:57 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.45 kb |
#include <stdio.h>
int const N=2000001;
bool c[N];
int ciur(int n)
{
int i,j;
for(i=2;i*i<=N;i++)
if(c[i]==false)
for(j=i*i;j<=n;j+=i)
c[j]=true;
return 0;
}
int main()
{
int i,n,cnt=0;
freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);
scanf("%d",&n);
ciur(n);
for(i=2;i<=n;i++)
if(c[i]==false) cnt++;
printf("%d",cnt);
return 0;
}