丑数问题

只包含因子2,3,5的树称之为丑数  ，查找指定位置的丑数

package offer;

public class choushu {
    public static boolean isugly(int num){
        if(num<=0){
            return false;
        }
        while(num%2==0){
            num/=2;
        }
        while(num%3==0){
            num/=3;
        }
        while(num%5==0){
            num/=5;
        }
        if(num==1)
            return true;
        else 
            return false;    
    }
    public static int findugly(int index){
        int num=0;
        int num_ug=0;
        while(num_ug<index){
            ++num;
            if(isugly(num)){
                num_ug++;
                
            }
        }
        return num;
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
System.out.println(findugly(7));
    }

}