String

5. Longest Palindromic Substring

this is WRONG, we can NOT use binary search here.

The following code can pass half of the test case and it is not correct as the number of length of

for example, we have the number of palindromic as 1 and 3 and we don’t have 2.

“aba”

class Solution:
    def longestPalindrome(self, s: str) -> str:
        if not s:return ""
        def good(m):
            for i in range(len(s)):
                if i+m<=len(s) and s[i:i+m][::-1] == s[i:i+m]:return True
            return False
        def binary():
            l, r = 1, len(s)
            while l<r:
                m = (l+r+1)//2
                if good(m):
                    l = m
                else:
                    r = m-1
            return l
        m = binary()
        for i in range(len(s)):
             if s[i:i+m][::-1] == s[i:i+m]:return s[i:i+m]