adding updates

src/my_project/interviews/google_top_exercises/round_1/12_longest_palindrome_substring.py

@@ -0,0 +1,25 @@
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        if len(s) < 2:
+            return s
+
+        start = 0
+        max_len = 1
+
+        def expand(left: int, right: int) -> None:
+            nonlocal start, max_len
+            # Expand outward while the substring stays a palindrome
+            while left >= 0 and right < len(s) and s[left] == s[right]:
+                left -= 1
+                right += 1
+            # Loop exits one step too far, so the palindrome is s[left+1 : right]
+            length = right - left - 1
+            if length > max_len:
+                max_len = length
+                start = left + 1
+
+        for i in range(len(s)):
+            expand(i, i)      # odd-length center
+            expand(i, i + 1)  # even-length center
+
+        return s[start:start + max_len]