[Leetcode] 9. Palindrome Number

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于 2017-01-26 12:48:31 发布

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分类专栏： LeetCode python 文章标签： leetcode

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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。通过将整数反转并与原数比较来实现，特别注意了负数的情况。

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Problem:

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

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.

思路：
方法和之前的判断回文数差不多。注意要加上对负数的判断。

Solution：

# -*- coding: utf-8 -*-
"""
Created on Tue Jan 24 01:01:47 2017

@author: liangsht
"""

class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        recordx = x
        posFlag = True if x >= 0 else False
        x = x if x >= 0 else -x
        result = 0
        while x != 0:
            tmp = x % 10
            result = result * 10 + tmp
            x = x / 10
        result = result if posFlag else -result
        if posFlag == False:
            return False
        return True if result == recordx else False