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+# 5. Longest Palindromic Substring
+
+"""
+given a string 's', return the longest palindromic substring in 's'
+"""
+
+
+class Solution(object):
+ def helper(self, s, l, r):
+ while l >= 0 and r < len(s) and s[l] == s[r]:
+ l -= 1
+ r += 1
+ return s[l + 1 : r]
+
+ def longestPalindrome(self, s):
+ ans = ""
+ for i in range(len(s)):
+ tmp = self.helper(s, i, i)
+ if len(tmp) > len(ans):
+ ans = tmp
+ tmp = self.helper(s, i, i + 1)
+ if len(tmp) > len(ans):
+ ans = tmp
+ return ans
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(obj.longestPalindrome("babad")) # expect: bab
+ print(obj.longestPalindrome("cbbd")) # expect: bb