Cod sursa(job #355347)

Utilizator andraiandra ionescu andrai Data 10 octombrie 2009 19:25:55
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 0.48 kb
#include<fstream.h>
int main()
{
   long long n,i,k,nr;
   char a[2000005];
   ifstream f("ciur.in");
   ofstream g("ciur.out");
   f>>n;
   a[1]=0;
   for(i=2;i<=n;i++)
     a[i]=1;
   for(i=2;i<=n/2;i++)
      {
        if(a[i]==1)
	  {
	     k=2*i;
	     while(k<=n)
	       {
	        a[k]=0;
                k+=i;
               }
	  }
      }
   nr=0;
   for(i=2;i<=n;i++)
      if(a[i]==1)
  	nr++;
   g<<nr;
   
   f.close();
   g.close();
return 0;
}