5. Longest Palindromic Substring

Given a string s, return the longest palindromic substring in s.

Example 1:

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

Example 2:

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

Example 3:

Input: s = "a"
Output: "a"

Example 4:

Input: s = "ac"
Output: "a"

Constraints:

• 1 <= s.length <= 1000
• s consist of only digits and English letters (lower-case and/or upper-case),

# @lc code=start
using LeetCode

function longest_palindrome(s::String)::AbstractString
    res = ""
    for i in 1:length(s)
        s_odd = _longest_palindrome(s, i, i)
        if length(s_odd) > length(res)
            res = s_odd
        end
        s_even = _longest_palindrome(s, i, i + 1)
        if length(s_even) > length(res)
            res = s_even
        end
    end
    return res
end

function _longest_palindrome(s, l, r)
    while l >= 1 && r <= length(s) && s[l] == s[r]
        l -= 1
        r += 1
    end
    return SubString(s, l + 1, r - 1)
end
# @lc code=end

_longest_palindrome (generic function with 1 method)

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