9/13 每日一題(尋找最長回文)

Given a string s, return the longest 

palindromic

 

substring

 in s.

 

Example 1:

Input: s = "babad"
Output: "bab"
Explanation: "aba" is also a valid answer.

Example 2:

Input: s = "cbbd"
Output: "bb"

 

Constraints:

• 1 <= s.length <= 1000
• s consist of only digits and English letters.

 class Solution:

    def longestPalindrome(self, s: str) -> str:

        n=0

        long=len(s)

        while long > 0:

            tes_list=s[n:n+long]

            if tes_list == tes_list[::-1] :

                print(f'抓到回文')

                print(tes_list)

                return "".join(tes_list)

            n+=1

            if n+long>len(s):

                '初始化, 進入下一輪'

                long -= 1

                n = 0

           

--------------------------------

class Solution:
    def longestPalindrome(self, s: str) -> str:
        if s == s[::-1]:
            return s
        start, size = 0, 1
        for i in range(1, len(s)):
            l, r = i - size, i + 1
            s1, s2 = s[l-1:r], s[l:r]
            if l >= 1 and s1 == s1[::-1]:
                size += 2
                start = l - 1
            elif s2 == s2[::-1]:
                size += 1
                start = l
        return s[start: start + size]