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:**

*   <code>1 <= digits.length <= 10<sup>4</sup></code>
*   `0 <= digits[i] <= 9`