(nur Verbindung zum Jury-Server)
International Collegiate Programming Contest
NWERC NEERC CERC SWERC SEERC |
String
\(\leftrightarrow\) ZahlString
\(\leftrightarrow\) char
-Feldimport java.util.Scanner; public class UpsideDownPrimes { static boolean isPrime(long n) { // brute-force-Primzahltest if ( n <= 1) return false; if ( n == 2 || n == 3) return true; for (int i = 2; i * i <= n; i++) if ( n % i == 0) return false; return true; } public static void main (String[] args) { Scanner input = new Scanner(System.in); String s = input.next(); int l = s.length(); char[] ca = s.toCharArray(), ac = new char[s.length()]; boolean flag = false; // '3', '4' oder '7' ? for (int i = 0; i < l; i++) // erst ziffernweise umdrehen .. switch (ca[i]) { case '6': ac[l-i-1] = '9'; case '9': ac[l-i-1] = '6'; case '3': case '4': case '7': flag = true; default: ac[l-i-1] = ca[i]; } // .. dann umgedrehten String erzeugen: String t = flag ? "0" : new String(ac); // Strings in Zahlen umwandeln und testen: long m = Long.parseLong(s), n = Long.parseLong(t); System.out.println((isPrime(n) && isPrime(m)) ? "yes":"no"); } }
"Algorithms for programming contests" (2 Sem.)