백준 4673 셀프넘버 ] 함수사용

        /*
         * 1 = 2
         * 2 = 4
         * 3 = 6
         * 4 = 8 
         * 5 = 10
         * ...
         * 10 = 11
         * 11 = 13
         * 13 = 17 
         * ...
         * 5000 = 5005
         * ...
         * 9950 = 9973
         * 9951 = 9974
         * ...
         * 9972 = 9999
         * 
         * */
        public class Main {
    public static void main(String[] args){

        int[] arr = new int[10000];//0으로 초기화
        for(int i = 1; i <= 10000; i++)
            if(dn(i)<10000) arr[dn(i)]++;

        for(int i = 1; i < 10000; i++)
            if(arr[i] == 0) System.out.println(i);
    }

    public static int dn(int n) {
        String nStr = Integer.toString(n);
        int result = n;
        for(int i = 0; i < nStr.length(); i++)
            result += Integer.parseInt(nStr.charAt(i)+"");

        return result;
    }
}