Cod sursa(job #187607)
Utilizator | Andrei Misarca Mishu91 | Data | 4 mai 2008 19:22:07 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.47 kb |
#include <cstdio>
#include <vector>
using namespace std;
int N;
void ciur()
{
int cnt = 1, M = (N - 1) >> 1;
vector <bool> V(M);
for(int i = 3; i<= N; i += 2)
{
if(V[i >> 1]) continue;
for(int j = i + (i >> 1); j <= M; j += i)
V[j] = 1;
++ cnt;
}
printf("%d\n",cnt);
}
int main()
{
freopen("ciur.in","rt",stdin);
freopen("ciur.out","wt",stdout);
scanf("%d",&N);
ciur();
}