Cod sursa(job #232839)
Utilizator | Data | 16 decembrie 2008 09:08:16 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.54 kb |
#include <fstream.h>
bool a[2000000];
int main()
{
int i, j, n, nr = 0;
ifstream fin("ciur.in");
fin >> n;
fin.close();
ofstream fout("ciur.out");
for ( i = 0; i < n; i++)
a[i] = true;
for ( i = 2; i * i <= n; i++)
if ( a[i] )
{
j = 2;
while ( i*j < n )
{
a[i*j] = false;
j++;
}
}
for ( i = 2; i <= n; i++)
if ( a[i] )
nr++;
fout << nr;
fout.close();
return 0;
}