Cod sursa(job #627451)
Utilizator | Data | 29 octombrie 2011 22:48:03 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 10 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.41 kb |
#include<fstream>
using namespace std;
int main(){
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");
int i, j, N, nr=1;
fin >> N;
int jum = N % 2 == 0 ? N / 2 - 1 : N / 2;
char v[jum+1];
for (i = 1; i <= jum; i++) v[i] = 1;
for (i = 1; i <= jum; i++)
if (v[i] == 1){
nr++;
for (j = 3*i + 1; j <= jum ; j += 2*i) v[j] = 0;
}
fout<<nr<<"\n";
fout.close();
return 0;
}