Cod sursa(job #356326)
Utilizator | Andrei matzipan | Data | 14 octombrie 2009 13:39:04 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.38 kb |
#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
unsigned int N,i;
char v[2000000];
long era() {
unsigned int x,nr,i;
nr=N-2;
for(i=2; i<=N; i++)
if(v[i]!=0)
for(x=2; x*i<N; x++)
if(v[x*i]!=0)
{ nr--; v[x*i]=0; }
return nr;
}
int main() {
in>>N;
for(i=2; i<=N; i++) v[i]=1;
out<<era();
return 0;
}