1332. Remove Palindromic Subsequences.cpp

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.

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: String is already palindrome
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".
Example 4:

Input: s = ""
Output: 0


Constraints:

0 <= s.length <= 1000
s only consists of letters 'a' and 'b'







class Solution {
public:

    bool isPalindrome(string s){
        int start=0, end=s.length()-1;
        while(start<end){
            if(s[start]!=s[end])
                return false;
            start++;
            end--;
        }
        return true;
    }

    int removePalindromeSub(string s) {
        if(s.length()==0) return 0;
        if(isPalindrome(s)) return 1;
        return 2;
    }
};

/*
If it's empty sting, return 0;
If it's palindrome, return 1;
Otherwise, we need at least 2 operation.

We can delete all characters 'a' in the 1st operation,
and then all characters 'b' in the 2nd operation.
So return 2 in this case
*/