O(n^2) time and O(n) space using DP

Author: 149ps

5. Longest Palindromic Substring/5. Longest Palindromic Substring.py

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+"""
+Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.
+
+Example 1:
+
+Input: "babad"
+Output: "bab"
+Note: "aba" is also a valid answer.
+Example 2:
+
+Input: "cbbd"
+Output: "bb"
+"""
+class Solution:
+    def longestPalindrome(self, s: str) -> str:
+        result = ''
+        def helper(s,l,r):
+            while l >= 0 and r < len(s) and s[l] == s[r]:
+                l -= 1
+                r += 1
+            return s[l+1:r]
+        for i in range(len(s)):
+            odd = helper(s,i,i)
+            even = helper(s,i,i+1)
+            result = max(result,odd,even,key = len)
+        return result