Largest Palindromic Number

Statement

You are given a string num consisting of digits from $0$ to $9$. Your task is to return the largest possible palindromic number as a string by using some or all of the digits in num. The resulting palindromic number must not have leading zeros.

Note: You may reorder the digits freely, and you must use at least one digit from the num string.

Constraints:

• $1\leq$ num.length $\leq 1000$

• num consists of digits

Example