palindrome-number.py

# -*- coding:utf-8 -*-


# Determine whether an integer is a palindrome. Do this without extra space.
#
# click to show spoilers.
#
# Some hints:
#
# Could negative integers be palindromes? (ie, -1)
#
# If you are thinking of converting the integer to string, note the restriction of using extra space.
#
# You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?
#
# There is a more generic way of solving this problem.


class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if x < 0:
            return False
        x = abs(x)
        l = len(str(x))
        i = 1
        while i < l / 2 + 1:

            head = (x / 10 ** (l-i)) % 10
            tail = (x % 10 ** i) if i == 1 else (x % 10 ** i) / (10 ** (i-1))
            if head != tail:
                return False
            i = i + 1

        return True