Sword To Offer 033 - 丑数

class Solution {
public:
    long long GetUglyNumber_Solution(int index) {
        if(index == 0) {
            return 0;
        }
        set<long long> s;
        int token = 0;
        s.insert(1);
        while(token + 1 < index) {
            auto currentPoint = s.begin();
            long long currentNumber = *currentPoint;
            s.erase(currentPoint);
            token++;
            s.insert(currentNumber * 2);
            s.insert(currentNumber * 3);
            s.insert(currentNumber * 5);
        }
        return *s.begin();
    }
};