动态规划实现丑数

public int GetUglyNumber_Solution(int index) {
       if(index <= 0) return 0;
        if(index == 1) return 1;
        int[] ret = new int[index];
        ret[0] = 1;
        int t2 = 0, t3 = 0, t5 = 0;
        for(int i = 1; i < index; i++){
            ret[i] = Math.min(ret[t2]*2, Math.min(ret[t3]*3,ret[t5]*5));
            if(ret[i] == ret[t2]*2) t2++;
            if(ret[i] == ret[t3]*3) t3++;
            if(ret[i] == ret[t5]*5) t5++;
        }
        return ret[index-1];
    }