public class Solution
extends Object
1363 - Largest Multiple of Three\.
Hard
Given an array of digits `digits`, return _the largest multiple of **three** that can be formed by concatenating some of the given digits in **any order**_. If there is no answer return an empty string.
Since the answer may not fit in an integer data type, return the answer as a string. Note that the returning answer must not contain unnecessary leading zeros.
**Example 1:**
**Input:** digits = [8,1,9]
**Output:** "981"
**Example 2:**
**Input:** digits = [8,6,7,1,0]
**Output:** "8760"
**Example 3:**
**Input:** digits = [1]
**Output:** ""
**Constraints:**
* 1 <= digits.length <= 104
* `0 <= digits[i] <= 9`