179. Largest Number
Given a list of non negative integers, arrange them such that they form the largest number.
Note: The result may be very large, so you need to return a string instead of an integer.
For two numbers a and b, if you convert them to strings, if ab> ba, then a will be ranked first,
For example, 9 and 34, since 934>349, 9 is in front,
For example, 30 and 3, because 303<330, 3 is in front of 30.
After sorting the original array according to this rule, converting each number into a string and then concatenating it is the final result.