string: add Palindromic Substrings

Author: theanujdev

string/palindromic_substrings.py

@@ -0,0 +1,32 @@
+# Palindromic Substrings (Medium)
+# Link - https://leetcode.com/problems/longest-palindromic-substring/
+
+# 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".
+
+
+class Solution:
+    def countSubstrings(self, s: str) -> int:
+        res = 0
+
+        def count_palindrome(l, r):
+            count = 0
+            while l >= 0 and r < len(s) and s[l] == s[r]:
+                count += 1
+                l -= 1
+                r += 1
+            return count
+
+        for i in range(len(s)):
+            res += count_palindrome(i, i)
+            res += count_palindrome(i, i+1)
+
+        return res