Longest Palindromic Substring problem ruby solution

Longest_Palindromic_Substring.rb

#Author: Shubham Mishra
#I/O: puts longest_palindrome("abbdbebffbebshsj")
#O/P: bebffbeb

def longest_palindrome(s)
    return s if s.length == 1
    st, en = 0, s.length - 1
    max = 0
    sub_s = ""
    sub_s_arr = []
    for i in st..(en - 1) do
        for j in (i+1)..en do
            if s[i] == s[j]
                sub_s_arr << [i,j]
            end
        end
    end
    sub_s_arr.sort_by! {|x| -(x[1] - x[0])}
    sub_s_arr.each do |ele_i|
        i = ele_i[0]
        j = ele_i[1]
        while i < j && s[i] == s[j] do
            i += 1
            j -= 1
        end
        if s[i] == s[j] && (j - i == 0 || i - j == 1)
            return s[ele_i[0]..ele_i[1]]
        end
    end
    return s[0]
end

puts longest_palindrome("abbdbebffbebshsj")