Leetcode-5

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Question

Solution1

遍历总长度。选定一个index后，建立两个指针，向左右两边遍历，判断是否相等。

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class Solution:
    def longestPalindrome(self, s: str) -> str:
        res = ''
        for i in range(len(s)):
            temp = self.helpper(s, i, i)
            if len(temp) > len(res):
                res = temp
            temp = self.helpper(s, i, i+1)
            if len(temp) > len(res):
                res = temp
        return res
    
    def helpper(self, s, l, r):
        while l >= 0 and r < len(s) and s[l] == s[r]:
            l -= 1
            r += 1
        return s[l+1:r]