丑数

class Solution {
public:
    int Min(int n1,int n2,int n3){
        int min = (n1 < n2) ? n1 : n2;
        min = (min < n3) ? min : n3;
        return min;
    }
    
	int GetUglyNumber_Solution(int index) {
        if(index < 1)
            return 0;
        int ugly[index];
        
        ugly[0] = 1;
        int next = 1;
     
        int index2 = 0;
        int index3 = 0;
        int index5 = 0;
        
     	while(next < index){
            int min = Min(ugly[index2]*2,ugly[index3]*3,ugly[index5]*5);
            ugly[next] = min;
            
            while(ugly[index2] * 2 <= min)
                index2++;
            while(ugly[index3] * 3 <= min)
                index3++;
            while(ugly[index5] * 5 <= min)
                index5++;
            
            next++;
        }
        return ugly[index-1];
	}
};