Cod sursa(job #2528854)
Utilizator | Kovac Vlastimil Vlaskov | Data | 22 ianuarie 2020 18:18:31 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.5 kb |
#include <bits/stdc++.h>
#define N 2000001
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n;
bool C[N];
void Ciur();
int main()
{
fin>>n;
int ct=0;
Ciur();
for(int i=2;i<=n;i++) if(!C[i]) ct++;
fout<<ct;
return 0;
}
void Ciur()
{
C[0]=C[1]=1;
for(int i=2;i<=n/2+1;i++)
{
if(!C[i])
{
for(int j=2;i*j<=n;j++)
{
C[i*j]=1;
}
}
}
}