5. 最长回文子串

5. 最长回文子串

 

方法一

class Solution(object):
    def longestPalindrome(self, s):
        """
        :type s: str
        :rtype: str
        """
        if s == "":
            return ""
        memo1 = []
        memo2 = []
        for (i,t) in enumerate(s):
            for j in range(i+1, len(s)):
                if s[len(s)+i-j] == t:
                    if s[i:len(s)-j+i+1] == s[i:len(s)-j+i+1][::-1]:
                        memo1.append([i,len(s)-j+i+1])
                        memo2.append(len(s)-j+1)
                        break
                        #return s[i:len(s)-j+i+1]
        if memo1 == []:
            return s[0]
        else:
            a = memo1[memo2.index(max(memo2))]
            return s[a[0]:a[1]]

 

方法二：Manacher 算法