Palindromic substrings

class Solution:
    def countSubstrings(self, s: str) -> int:
        res = 0
        for i in range(len(s) + 1):
            for j in range(i):
                st = s[j:i]
                if st[::-1] == st:
                    res += 1

        return res

Palindromic Substrings

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Given a string s, return the number of palindromic substrings in it.

A string is a palindrome when it reads the same backward as forward.

A substring is a contiguous sequence of characters within the string.

 

Example 1:

Input: s = "abc"
Output: 3
Explanation: Three palindromic strings: "a", "b", "c".

Example 2:

Input: s = "aaa"
Output: 6
Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".

 

Constraints:

• 1 <= s.length <= 1000
• s consists of lowercase English letters.