9. Palindrome Number-python

本文介绍了一种不使用额外空间判断整数是否为回文的方法。通过计算位数并逆序比较来实现,讨论了负数及整数溢出等问题。

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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?

Code

class Solution(object):
    def isPalindrome(self, x):
        """
        :type x: int
        :rtype: bool
        """
        palindromex = 0
        tmp = x
        sumbit = 0
        #calcuate bit count
        while tmp > 0:
            sumbit+=1
            tmp /= 10
        tmp = x;
        #get a number reversely
        while tmp > 0:
            sumbit-=1
            palindromex += tmp % 10 * 10**sumbit
            tmp /= 10
        return palindromex == x
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