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.
SOLUTION:
class Solution:
def countSubstrings(self, s: str, i = 0) -> int:
n = len(s)
if i == n - 1:
return 1
k = self.countSubstrings(s, i + 1)
ctr = 0
for j in range(i + 1, n + 1):
if s[i:j] == s[i:j][::-1]:
ctr += 1
return ctr + k
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