solve: longest palindromic substring

Author: sounmind

longest-palindromic-substring/evan.py

@@ -0,0 +1,25 @@
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        if not s:
+            return ""
+
+        start, end = 0, 0
+
+        def expand_and_get_length(s, left, right):
+            while left >= 0 and right < len(s) and s[left] == s[right]:
+                left -= 1
+                right += 1
+
+            return right - left - 1
+
+        for i in range(len(s)):
+            odd_palindrome_length = expand_and_get_length(s, i, i)
+            even_palindrome_length = expand_and_get_length(s, i, i + 1)
+
+            max_len = max(odd_palindrome_length, even_palindrome_length)
+
+            if max_len > end - start:
+                start = i - (max_len - 1) // 2
+                end = i + max_len // 2
+
+        return s[start : end + 1]