給定一字符數組,求數組中字符組成的所有排列

public static void main(String[] args)
    {
        char[] origin = { 'a', 'b', 'c', 'd', 'e', 'f' };
        int length = origin.length;
        int[] tmp = new int[length];
        char[] res = new char[length];
        boolean[] check = new boolean[length];
        int index = 0, level = 0;
        while (true)
        {
            if (index >= 0 && index < length && level >= 0 && level < length)
            {
                if (!check[index])
                {
                    tmp[level] = index;
                    res[level] = origin[index];
                    check[index] = true;
                    level++;
                    index = 0;
                }
                else
                {
                    index++;
                }
            }
            else if (level >= length)
            {
                System.out.println(new String(res));
                level = length - 1;
                index = tmp[level];
                check[index] = false;
                index++;
            }
            else if (index >= length)
            {
                level--;
                if (level < 0)
                    break;
                index = tmp[level];
                check[index] = false;
                index++;
            }
            else
            {
                break;
            }
        }
    }