[leetcode]Palindrome Number @ Python

原題地址：https://oj.leetcode.com/problems/palindrome-number/

題意：

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.

解題思路：不允許用額外空間，所以不能將數轉換成字符串來判斷。這里有一種精巧的解決方式。

代碼：

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