[leetcode]Palindrome Number @ Python

原题地址：https://oj.leetcode.com/problems/palindrome-number/

题意：

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.

解题思路：不允许用额外空间，所以不能将数转换成字符串来判断。这里有一种精巧的解决方式。

代码：

class Solution:
    # @return a boolean
    def isPalindrome(self, x):
        if x < 0:
            return False
        div = 1
        while x/div >= 10:
            div = div * 10
            
        while x:
            left = x / div
            right = x % 10
            
            if left != right:
                return False
            
            x = ( x % div ) / 10
            div = div / 100
        return True