@Override
        public int compareTo(Node other) {
            return this.val - other.val;
        }
Date 03/08/2016
@author Tushar Roy

Find nth ugly number.

https://leetcode.com/problems/ugly-number-ii/
https://leetcode.com/problems/super-ugly-number/
http://www.geeksforgeeks.org/ugly-numbers/
src/com/interview/dynamic/UglyNumbers.java