Cod sursa(job #627453)
Utilizator | Mihai Bogdan mihaibogdan10 | Data | 29 octombrie 2011 23:42:57 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.44 kb |
#include<fstream>
using namespace std;
int main(){
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");
int i, j, N, nr=1, k;
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++;
k = i * 2 + 1;
for (j = 3 * k; j <= N ; j += 2*k)
v[j / 2] = '0';
}
fout<<nr<<"\n";
fout.close();
return 0;
}