Cod sursa(job #561376)

Utilizator devill_08Buli.vlad devill_08 Data 19 martie 2011 23:43:34
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.35 kb
Raporteaza aceasta sursa 
#include <cstdio>

long n,i,nr,j;
char prim[2000000];

int main ()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%ld", &n);
	prim[2]=1;
	for(i=3;i<=n;i+=2) prim[i]=1;
	for(i=2;i<=n/2;i++)
		if(prim[i])
			for(j=i+i;j<=n;j+=i) prim[j]=0;
	for(i=1;i<=n;i++)
		if(prim[i]==1) nr++;
	printf("%ld", nr);
	return 0;
}