Cod sursa(job #2751826)

Utilizator matei.balaur2009Matei Balaur12 matei.balaur2009 Data 15 mai 2021 21:30:52
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.34 kb
Raporteaza aceasta sursa 

#include <iostream>
#include <fstream>
#include <bitset>
using namespace std;
#define MAXN 2000000
int N;
bitset<MAXN> b;
int main()
{
    ifstream fin("ciur.in");
    ofstream fout("ciur.out");
    fin>>N;
    int i, j;
    for (i=3;i*i<=N;i+=2)
        if (!b[i]) for (j=i*i;j<=N;j+=2*i) b[j]=1;
   fout<<(N+1)/2-b.count()<<'\n';
}