Cod sursa(job #556010)
Utilizator | So Damn Good sodamngood | Data | 15 martie 2011 21:26:24 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.49 kb |
#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
#define maxn 2000010
int N, sol;
bool prim[maxn];
int main() {
FILE *f1=fopen("ciur.in", "r"), *f2=fopen("ciur.out", "w");
int i, j;
fscanf(f1, "%d\n", &N);
for(i=2; i<=N; i++) {
if(!prim[i]) {
sol ++;
for(j=2*i; j<=N; j+=i) {
prim[j] = 1;
}
}
}
fprintf(f2, "%d\n", sol);
fclose(f1); fclose(f2);
return 0;
}