[leetcode]Palindrome Number @ Python

最新推荐文章于 2025-09-06 22:33:46 发布

weixin_34081595

最新推荐文章于 2025-09-06 22:33:46 发布

阅读量70

点赞数

文章标签：数据结构与算法 python

本文介绍了一种不使用额外空间判断整数是否为回文数的方法，并提供了一个Python实现示例。该方法巧妙地避免了将整数转换为字符串的过程。

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