Tìm Palindrome dài nhất trong một mảng

def longest_palindrome_opt(arr):
    def is_palindrome(n):
        if n < 0: return False
        temp, rev = n, 0
        while temp > 0:
            rev = rev * 10 + (temp % 10)
            temp //= 10
        return n == rev
    
    longest = -1
    for num in arr:
        if is_palindrome(num):
            if longest == -1 or num > longest:
                longest = num
    return longest

def longest_palindrome_brute(arr):
    def is_palindrome(n):
        s = str(n)
        return s == s[::-1]
    
    res = -1
    for num in arr:
        if is_palindrome(num):
            if res == -1 or len(str(num)) > len(str(res)):
                res = num
    return res