LeetCode5：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 1:

Input: "babad"
Output: "bab"
Note: "aba" is also a valid answer.

Example 2:

Input: "cbbd"
Output: "bb"

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LeetCode：链接

参考链接：LeetCode647：Palindromic Substrings

647是找出所有的回文字符串，这道题是找到最长的回文字符串，思路都是一样的。

class Solution(object):
    def longestPalindrome(self, s):
        """
        :type s: str
        :rtype: str
        """
        n = len(s)
        if n == 0:
            return ""
        dp = [[0] * n for i in range(n)]
        dp[0][0] = 1 
        length = 1
        result = s[0]
        for i in range(1, n):
            for j in range(i):
                # (i-j < 2)这个最好要封口
                dp[j][i] = (s[i] == s[j]) & ((i-j < 2) | dp[j+1][i-1])
                if dp[j][i] and (i-j+1) > length:
                    length = i-j+1
                    result = s[j:i+1]
            dp[i][i] = 1
        return result