#647

Palindromic Substrings

medium· 1-D DPruns: 0

Given a string s, return the number of palindromic substrings in it. A string is palindromic if it reads the same forward and backward. Different start or end indices count as different substrings even if they consist of the same characters.

wpm 0acc 100%time 0:000 / 456

class Solution:
    def countSubstrings(self, s: str) -> int:
        count = 0

        def expand(left: int, right: int) -> int:
            local = 0
            while left >= 0 and right < len(s) and s[left] == s[right]:
                local += 1
                left -= 1
                right += 1
            return local

        for i in range(len(s)):
            count += expand(i, i)
            count += expand(i, i + 1)
        return count

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