(python)leetcode刷题笔记05 Longest Palindromic Substring

5. 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"

class Solution:
    def solve(self,s,l,r):
        while r<len(s) and l>=0 and s[l]==s[r]:
            l-=1
            r+=1
        return s[l+1:r]
    def longestPalindrome(self,s):
        if len(s) == 0:
            return 0
        max_string=''
        for i in range(len(s)):
            #奇数长度回文串如ababa
            tmp=self.solve(s,i,i)
            if len(tmp)>len(max_string):
                max_string=tmp
            #偶数回文串如abba

            tmp=self.solve(s,i,i+1)
            if len(tmp)>len(max_string):
                max_string=tmp

        return max_string

def solve(s,l,r):
    while r<len(s) and l>=0 and s[l]==s[r]:
        l-=1
        r+=1
    return s[l+1:r]
def longestPalindrome(s):
    if len(s) == 0:
        return 0
    max_string=''
    for i in range(len(s)):
        #奇数长度回文串如ababa
        tmp=solve(s,i,i)
        if len(tmp)>len(max_string):
            max_string=tmp
        #偶数回文串如abba

        tmp=solve(s,i,i+1)
        if len(tmp)>len(max_string):
            max_string=tmp

    return max_string




print(longestPalindrome('ababa'))