查找字符串最长回文

Longest Palindromic Substring

• Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000.

• Example:

Input: "babad"
Output: "bab"

• Note: "aba" is also a valid answer.

• Example:

Input: "cbbd"
Output: "bb"

思路

1. 回文有奇回文和偶回文&＃xff0c;abcba是奇回文&＃xff0c;abccba是偶回文

2. 回文都是中心对称&＃xff0c;找到对称点后&＃xff0c;同时向前后寻找回文的最长串即可

3. 奇回文和偶回文可以归为同一种情况&＃xff0c;即abcba以c为对称点&＃xff0c;abccba以cc为对称点&＃xff0c;但为了代码可读性&＃xff0c;可以分开讨论

代码

class Solution(object):def longestPalindrome(self, s):""":type s: str:rtype: str"""self.maxlen &＃61; 0self.retstr &＃61; &＃39;&＃39;if len(s) <2:return sfor i in range(len(s)):self.__find_palindrome(s, i, i) #奇回文self.__find_palindrome(s, i, i&＃43;1) #偶回文return self.retstrdef __find_palindrome(self, s, j, k):while j >&＃61; 0 and k

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