Cod sursa(job #1479953)
Utilizator | Data | 1 septembrie 2015 18:29:13 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.42 kb |
#include <fstream>
#include <bitset>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int n,i,j,cnt=1;
bitset<2000010> v;
int main()
{
f>>n;
for (i=3;i*i<=n;i+=2)
if(!v[i])
{
cnt++;
for(j=i*i;j<=n;j+=2*i)
v[j]=1;
}
for(;i<=n;i+=2)
if(!v[i])
cnt++;
g<<cnt<<'\n';
return 0;
}