Cod sursa(job #539584)

Utilizator constantinsorinconstantin sorin constantinsorin Data 23 februarie 2011 08:42:16
Problema Ciurul lui Eratosthenes Scor 0
Compilator cpp Status done
Runda Arhiva educationala Marime 0.33 kb
Raporteaza aceasta sursa 
#include<fstream.h>
ifstream fin("ciur.in");
ofstream fout("ciur.out");
long n;
unsigned char a[2000001];
int main()
{
	long i,j,nr,sw;nr=0;
	fin>>n;
	memset(a,1,sizeof(a));
	a[1]=0;a[0]=1;
	for(i=2;i*i<=n;i++)
		if(a[i]==0)
		 for(j=2*i;j<=n;j=j+i)
			a[j]=1;
	for(i=2;i<=n;i++)
		if(a[i])nr++;
	fout<<nr;
	return 0;
}