Cod sursa(job #2572652)
Utilizator | Sebastian Cojocaru Sebaschan | Data | 5 martie 2020 13:43:04 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.51 kb |
#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n, c[2000001];
void makeCiur(int v[]) {
for(int i = 2; i*i <= n; i++) {
for(int j = 2; j <= n/i; j++) {
c[i*j] = i*j;
}
}
}
int primeNr(int n) {
int nr = 0;
for(int i = 2; i <= n; i++)
if(c[i] == 0)
nr++;
return nr;
}
int main() {
fin>>n;
makeCiur(c);
fout<<primeNr(n);
return 0;
}