Cod sursa(job #792420)
Utilizator | Pregatire Concurs preg_concurs | Data | 27 septembrie 2012 10:29:07 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.52 kb |
#include<fstream>
#define M 2000001
using namespace std;
FILE *f, *g;
int main()
{
int i, j, n, cont=0;
char p[M];
f=fopen("ciur.in", "r");
g=fopen("ciur.out", "w");
fscanf(f, "%d", &n);
for(i=2; i<=n; i++)
p[i]='1';
for(i=2; i<=n; i++)
if(p[i]=='1')
{
cont++;
for(j=i*i; j<=n; j+=i)
p[j]='0';
}
fprintf(g, "%d\n", cont);
fclose(f);
fclose(g);
return 0;
}