Cod sursa(job #1970706)
Utilizator | Data | 19 aprilie 2017 15:47:00 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.42 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int n,ciur[2000001],nr;
void construct_ciur()
{
ciur[1]=1;
for(int i=2;i*i<=n;++i)
if(!ciur[i])
for(int j=i*i;j<=n;j+=i)
ciur[j]=1;
}
int main()
{
f>>n;
construct_ciur();
for(int i=2;i<=n;i++)
if(!ciur[i])
nr++;
g<<nr;
return 0;
}