Java prime number
A prime number is a number that can no longer be divided equally. For example: 2 3 5 7 11 etc.
9 = 3 * 3 means that it divides into 3 and is therefore not prime.
Our country was founded in 1949. If you are only given the 4 number cards 1 9 4 9,
you can place them in any order (but the cards can't be placed upside down, we are not brain teasers!),
then, how many 4 digits can you form? What about prime numbers?
public static void main(String[] args) {
HashSet<Integer> set = new HashSet<Integer>();
int temp;
for (int i = 1499; i <= 9941; i++) {
String str = String.valueOf(i);
char[] c = str.toCharArray();
Arrays.sort(c);
str = String.valueOf(c);
if (str.equals("1499")) {
set.add(i);
}
}
Iterator<Integer> iter = set.iterator();
while (iter.hasNext()) {
temp = iter.next();
if (GetNum(temp)) {
System.out.println(temp);
}
}
}
public static boolean GetNum(int n) {
for (int i = 2; i < n; i++) {
if (n % i == 0)
return false;
}
return true;
}