java 任意花朵数算法

/** * 花朵数，网友算法下载学习 * @author cxcx * */public class Arithmetic11 {    private static BigInteger[] table = new BigInteger[10];     public static void main(String[] args) {        long time = System.nanoTime();        find(21);        time = System.nanoTime() - time;        System.out.println(time / 1000000000.0 + "s");    }     public static void find(int n) {        for (int i = 0; i < 10; i++)            table[i] = BigInteger.valueOf(i).pow(n);        int[] nums = new int[n];        int index = 0;        int num = 0;        BigInteger sum = BigInteger.ZERO;        BigInteger MIN = BigInteger.TEN.pow(n - 1);        BigInteger MAX = BigInteger.TEN.pow(n).subtract(BigInteger.ONE);        while (true) {            if (index < nums.length && num < 10) {                BigInteger temp = sum.add(table[num]);                if (temp.compareTo(MAX) < 0) {                    nums[index] = num;                    index++;                    sum = temp;                    continue;                }            } else if (index >= nums.length && sum.compareTo(MIN) > 0) {                int[] temp = getArray(sum);                if (check(nums, true, temp, false))                    System.out.println(sum);            } else if (index <= 0) {                break;            }            index--;            num = nums[index];            sum = sum.subtract(table[num]);            num++;        }    }     public static boolean check(int[] a1, boolean copy1, int[] a2, boolean copy2) {        if (a1.length != a2.length)            return false;        if (copy1)            a1 = a1.clone();        if (copy2)            a2 = a2.clone();        Arrays.sort(a1);        Arrays.sort(a2);        return Arrays.equals(a1, a2);    }     public static int[] getArray(BigInteger big) {        String s = String.valueOf(big);        int length = s.length();        int[] res = new int[length];        for (int i = 0; i < length; i++)            res[i] = s.charAt(i) - '0';        return res;    }}

算法参考：http://bbs.csdn.net/topics/360185693