Given a string s, return all the palindromic permutations (without duplicates) of it.
You may return the answer in any order. If s has no palindromic permutation, return an empty list.
Example 1:
Input: s = "aabb"
Output: ["abba","baab"]
Example 2:
Input: s = "abc"
Output: []
Constraints:
1 <= s.length <= 16s consists of only lowercase English letters.