Julekalender 2014

luke8.c

#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <sys/time.h>
#include <sys/stat.h>



bool primes[50];

void fillSieve() {
     primes[0] = primes[1] = true;
     for (int i = 2; i < 50; i++) {
         if (!primes[i]) {
             for (int j = 2; i * j < 50; j++) {
                 primes[i * j] = true;
             }
         }
     }
 }

bool isPrime(int n) {
     return !(primes[n]);
 }

 int getPerfectNumber(int prime) {
     return (int) (((2 << (prime - 2))) * ((2 << (prime-1)) - 1));
 }


 int main() {

     int LIMIT = 10000;
     fillSieve();
     for (int i = 2; i <= LIMIT; i++) {

         if (isPrime(i)) {
             int x = getPerfectNumber(i);
             if (x <= LIMIT) {
                 printf("%d,", x);
             } else {
                 return 0;
             }
         }
     }

 }