Self Numbers-蒲公英云

Self Numbers

2.Self Numbers

Description
In 1949 the Indian mathematician D.R. Kaprekar discovered a class of numbers
called self-numbers. For any positive integer n, define d(n) to be n plus 
the sum of the digits of n. (The d stands for digitadition, a term coined 
by Kaprekar.) For example, d(75) = 75 + 7 + 5 = 87. Given any positive
integer n as a starting point, you can construct the infinite increasing 
sequence of integers n,d(n), d(d(n)), d(d(d(n))), .... For example, if you
start with 33, the next number is 33 + 3 + 3 = 39, the next is 39 + 3 + 9 = 51, the next is 51 + 5 + 1 = 57,
and so you generate the sequence 33, 39, 51, 57, 69, 84, 96, 111, 114, 120, 
123, 129, 141, ... The number n is called a generator of d(n). In the sequence above, 33 is
a generator of 39, 39 is a generator of 51, 51 is a generator of 57, and 
so on. Some numbers have more than one generator: for example, 101 has two
generators, 91 and 100. A number with no generators is a self-number. 
There are thirteen self-numbers less than 100: 1, 3, 5, 7, 9, 20, 31, 42,
53, 64, 75, 86, and 97. 
Input
No input for this problem.
Output
Write a program to output all positive self-numbers less than 10000 in
increasing order, one per line. 
Sample Input
Sample Output
1
3
5
7
9
20
31
42
53
64
 |
 |       <-- a lot more numbers
 |
9903
9914
9925
9927
9938
9949
9960
9971
9982
9993

挺简单的

public class Main {
    public static void main(String[] args) {
        int a=1,b=1,c=3;
        int []arr=new int[10009];
        while(a<10000) {
            if(a<10) {
                arr[a+a%10]=1;
            }
            if(a<100) {
                arr[a+a%10+a/10]=1;
            }
            if(a<1000) {
                arr[a+a/100+a/10%10+a%10]=1;
            }
            if(a<10000) {
                if (a+a/100%10+a/1000+a/10%10+a%10>10000) {
                    break;
                }
                arr[a+a/100%10+a/1000+a/10%10+a%10]=1;
            }
            a++;
        }
        for(int i=1;i<9995;i++) {
            if (arr[i]==0) {
                System.out.println(i);
            }
        }
    }
}