Cod sursa(job #2682217)

Utilizator Marius05Voina Marius Marius05 Data 8 decembrie 2020 07:58:33
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.33 kb
Raporteaza aceasta sursa 
#include <iostream>
#include <fstream>
#include <bitset>
using namespace std;
#define maxn 2000000
int N;
bitset<maxn> b;
int main()
{
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    f>>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;
    g<<(N+1)/2-b.count()<<'\n';
}