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 in python:
class Solution:
def removePalindromeSub(self, s: str) -> int:
def isPalindrome(s):
i, j = 0, len(s)-1
while i < j:
if s[i] == s[j]:
i += 1
j -= 1
else:
return False
return True
if not s:
return 0
elif isPalindrome(s):
return 1
else:
return 2
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