1332. Remove Palindromic Subsequences

Problem

You are given a string s consisting only of letters 'a' and 'b'. In a single step you can remove one palindromic subsequence from s.

Return **the *minimum* number of steps to make the given string empty**.

A string is a subsequence of a given string if it is generated by deleting some characters of a given string without changing its order. Note that a subsequence does not necessarily need to be contiguous.

A string is called palindrome if is one that reads the same backward as well as forward.

  Example 1:

Input: s = "ababa"
Output: 1
Explanation: s is already a palindrome, so its entirety can be removed in a single step.

Example 2:

Input: s = "abb"
Output: 2
Explanation: "abb" -> "bb" -> "". 
Remove palindromic subsequence "a" then "bb".

Example 3:

Input: s = "baabb"
Output: 2
Explanation: "baabb" -> "b" -> "". 
Remove palindromic subsequence "baab" then "b".

  Constraints:

• 1 <= s.length <= 1000

• s[i] is either 'a' or 'b'.

Solution (Java)

class Solution {
    public int removePalindromeSub(String s) {
        if (s.isEmpty()) {
            return 0;
        }
        if (s.equals((new StringBuilder(s)).reverse().toString())) {
            return 1;
        }
        return 2;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).