剑指offer 丑数

class Solution {
public:
    int GetUglyNumber_Solution(int index) {
        if(index<=0) return 0;
        if(index==1) return 1;
        vector<int>k(index);
        k[0]=1;
        int t2=0,t3=0,t5=0;
        for(int i=1;i<index;i++)
        {
            k[i]=std::min(k[t2]*2,std::min(k[t3]*3,k[t5]*5));
            if(k[i]==k[t2]*2) t2++;
            if(k[i]==k[t3]*3) t3++;
            if(k[i]==k[t5]*5) t5++;
        }
        return k[index-1];
    }
};