折腾了两天了，一直只是通过测试，但是提交的时候会出错，代码效率太差。求大神指点...
算法如下：
*"Consider a sequence u where u is defined as follows:
The number u(0) = 1 is the first one in u.
For each x in u, then y = 2 x + 1 and z = 3 x + 1 must be in u too.
There are no other numbers in u.
Ex: u = [1, 3, 4, 7, 9, 10, 13, 15, 19, 21, 22, 27, ...]
1 gives 3 and 4, then 3 gives 7 and 10, 4 gives 9 and 13, then 7 gives 15 and 22 and so on..."*

我的代码如下`

public static int dblLinear(int n)
{
    ArrayList arrayresult = new ArrayList();
    arrayresult.add((long) 1);
    //循环，生成这样的u[]数组。但是i太大的话，会超时
    for (int i = 1; i <= 15; i++)
    {
        arrayresult = CreateArrayList(arrayresult);
    }
    System.out.println(arrayresult.toString());
    long location = arrayresult.get(n);
    return  (int)location;
}

public static ArrayList CreateArrayList(ArrayList resultArray)
{
    ArrayList tmp = (ArrayList)resultArray.clone();
    for (long single : resultArray)
    {
        //按照规则，生成y和z。
        long y = single * 2 + 1;
        long z = single * 3 + 1;
        //看看y和z在不在数组里面，不在的话，添加进去。
        if (resultArray.indexOf(y) == -1)
        {
            tmp.add(y);
        }
        if (resultArray.indexOf(z) == -1)
        {
            tmp.add(z);
        }
    }
    Collections.sort(tmp);
    return tmp;
}

public static void main(String[] args)
{
    System.out.println(DoubleLinear.dblLinear(100));
}`

提示错误："Process was terminated. It took longer than 10000ms to complete
0 Passed"

如果循环的i设置的小，那么数组里面的数字也不完整。归根到底，还是代码效率太差...求指导啊