这道题很容易想到需要根据数字的字符串大小进行倒序排列（目的是将首个数字比较大的数字排在前面）。很容想到需要自定义 Comparator。最简单省事的方式就是直接将排序的两个字符串相加（左右，右左）进行比较就可以了。
Given a list of non negative integers, arrange them such that they form the largest number.
Example 1:
Input: [10,2]
Output: "`210"`
Example 2:
Input: [3,30,34,5,9]
Output: "`9534330"`
Note: The result may be very large, so you need to return a string instead of an integer.
link:{sourcedir}/_0179_LargestNumber.java[role=include]