2193 - Minimum Number of Moves to Make Palindrome\.

Hard

You are given a string s consisting only of lowercase English letters.

In one move , you can select any two adjacent characters of s and swap them.

Return the minimum number of moves needed to make s a palindrome.

Note that the input will be generated such that s can always be converted to a palindrome.

Example 1:

Input: s = "aabb"

Output: 2

Explanation:

We can obtain two palindromes from s, "abba" and "baab".

• We can obtain "abba" from s in 2 moves: "aabb" -> "abab" -> "abba".

• We can obtain "baab" from s in 2 moves: "aabb" -> "abab" -> "baab".

Thus, the minimum number of moves needed to make s a palindrome is 2.

Example 2:

Input: s = "letelt"

Output: 2

Explanation:

One of the palindromes we can obtain from s in 2 moves is "lettel".

One of the ways we can obtain it is "letelt" -> "letetl" -> "lettel".

Other palindromes such as "tleelt" can also be obtained in 2 moves.

It can be shown that it is not possible to obtain a palindrome in less than 2 moves.

Constraints:

• 1 <= s.length <= 2000

• s consists only of lowercase English letters.

• s can be converted to a palindrome using a finite number of moves.