Python solution for Longest palindromic substring

Author: dsrao711

DSA 450 GFG/LongestPalindromicSubstring.py

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+#https://leetcode.com/problems/longest-palindromic-substring/
+
+class Solution(object):
+    def longestPalindrome(self, s):
+        """
+        :type s: str
+        :rtype: str
+        """
+        
+        # result to store palindrome
+        res = ""
+
+        for i in range(len(s)):
+
+            # for odd len strings
+            # Eg : "racecar"
+            tmp = self.helper(i, i, s)
+            if len(res) < len(tmp):
+                res = tmp
+
+            # for even len strings
+            # Eg: "aaaabbaa"
+            tmp = self.helper(i, i + 1, s)
+            if len(res) < len(tmp):
+                res = tmp
+
+
+        return res
+
+    def helper(self, l, r, s):
+    # Helper function to check if the left pointer and right pointer are equal 
+    # if inbound and palindrome, move left left and right right
+        
+        while (l >= 0 and r < len(s) and s[l] == s[r]):
+            l -= 1
+            r += 1
+
+ 
+        return s[l + 1: r]