Palindrome Number

Question

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

Tags

• Mathematics

Thought

Since we cannot use extra space, thus, stack, string, list are all not proper here. Instead, we can utilize the characteristic of the palindrome number here:

The order of the digits from left to right and from right to left should be the same. Thus, we can generate a new integer which is obtained according to the order of the digits in reversed order of the input integer.

Code

class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        if x < 0:
            return False
        if x == 0:
            return True
        y = 0
        tmp = x
        while tmp > 0:
            y = y * 10 + tmp % 10
            tmp /= 10
        return x == y