1332. Remove Palindromic Subsequences

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'

这题有点坑，注意了是subsequence，子序列，而不是子串，被这个坑了半天。

class RemovePalindromicSubsequences : public Solution {
public:
    void Exec() {
        auto res = removePalindromeSub("bbaabaaa");
    }
    bool isPalindromeLen(string s) {
        for (int i = 0; i < s.length() / 2; i++) {
            if (s[i] != s[s.length() - 1 - i]) {
                return false;
            }
        }
        return true;
    }
    int removePalindromeSub(string s) {
        int count = 0;
        if (s.empty()) {
            return count;
        }
        if (isPalindromeLen(s)) {
            return 1;
        }
        return 2;
    }
};