Cod sursa(job #948106)
Utilizator | Data | 9 mai 2013 14:57:19 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.52 kb |
#include <stdio.h>
#include <iostream>
using namespace std;
#define MAXSIZE 2000000/2+1
char p[MAXSIZE];
int Primes_3(int n)
{
int i, j, nr = 1;
for (i = 1; 2*i+1 <= n; i++)
if (p[i] == 0)
{
nr++;
for (j = 3*i+1; 2*j+1 <= n; j += 2*i+1)
p[j] = 1;
}
return nr;
}
int main()
{
freopen("ciur.in", "r", stdin);
freopen("ciur.out", "w", stdout);
int N;
cin >> N;
cout << Primes_3(N) << '\n';
return 0;
}