Given a string s, return all the palindromic permutations (without duplicates) of it. Return an empty list if no palindromic permutation could be form. 先用map來整理出所有char的個數，檢查一下char是否有兩個以上的奇數，若是的話 ...

In this problem, we need to implement a recursive function. We declare an array called ans and a variable num to record the beautiful permutations found so far. The cur array represents the array we ...