剑指 33.时间空间效率的平衡 丑数

public int GetUglyNumber_Solution(int index) {
         if (index<=0) {
            return 0;
        }
         ArrayList<Integer> list=new ArrayList<Integer>();
         list.add(1);
         int i2=0,i3=0,i5=0;
         while (list.size()<index) {
            int m2=list.get(i2)*2;
            int m3=list.get(i3)*3;
            int m5=list.get(i5)*5;
            int min=Math.min(m2, Math.min(m3, m5));
            list.add(min);
            if (min==m2)i2++;
            if (min==m3)i3++;
            if (min==m5)i5++;
        }
         
            return list.get(list.size()-1);

}