LeetCode Blog for course "Algorithms" -- Problem 9

Problem 9. Palindrome Number

Determine whether an integer is a palindrome. Do this without extra space.

My solution in Python:

class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if x < 0:
            return False
        copy, reverse = x, 0

        while copy:
            reverse *= 10
            reverse += copy % 10
            copy /= 10

        return x == reverse

Review:

After much thought, I cannot solve the problem without using extra space, so my solution does use some extra space as a new integer is constructed.
Negative numbers cannot be palindromic due to the preceding "-" sign which doesn't exist at the end, so we first check whether the given number is less than 0.
If it is greater than or equals 0, we construct a reversed version of this integer, then compare them. If the original integer equals to its reversed version, then the number is palindromic.