Cod sursa(job #236482)
Utilizator | Vlad Schnakovszki shnako | Data | 27 decembrie 2008 18:39:24 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 0 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.57 kb |
#include <fstream.h>
#include <math.h>
ifstream f("ciur.in");
ofstream g("ciur.out");
long v[20000], n, i, s=1, d, k;
int main()
{
f>>n;
for (i=2;i<=n;i++)
v[i]=1;
k=2;
d=k;
while (d<=n/k)
{
v[k*d]=0;
d++;
}
for (i=3;i<=sqrt(n);i=i+2)
if (v[i])
{
s++;
k=i;
d=k;
while (d<=n/k)
{
v[k*d]=0;
d++;
}
}
for (d=i+1;d<=n;d++)
if (v[d]==1)
s++;
g<<s;
f.close();
g.close();
return 0;
}