647. Palindromic Substrings .py

class Solution:
    def countSubstrings(self, s: str) -> int:
        n = len(s)
        palindrome = [[False] * n for _ in range(n)]
        ans = 0

        for i in range(n):
            palindrome[i][i] = True
            ans += 1

        for i in range(n - 1):
            if s[i] == s[i + 1]:
                palindrome[i][i + 1] = True
                ans += 1

        for length in range(3, n + 1):
            for i in range(n - length + 1):
                if s[i] == s[i + length - 1] and palindrome[i + 1][i + length - 2]:
                    palindrome[i][i + length - 1] = True
                    ans += 1

        return ans