1682. Longest Palindromic Subsequence II

A subsequence of a string s is considered a good palindromic subsequence if:

• It is a subsequence of s.
• It is a palindrome (has the same value if reversed).
• It has an even length.
• No two consecutive characters are equal, except the two middle ones.

For example, if s = "abcabcabb", then "abba" is considered a good palindromic subsequence, while "bcb" (not even length) and "bbbb" (has equal consecutive characters) are not.

Given a string s, return the length of the longest good palindromic subsequence in s.

Example 1:

Input: s = "bbabab"
Output: 4
Explanation: The longest good palindromic subsequence of s is "baab".

Example 2:

Input: s = "dcbccacdb"
Output: 4
Explanation: The longest good palindromic subsequence of s is "dccd".

Constraints:

• 1 <= s.length <= 250
• s consists of lowercase English letters.