转自Kindem的博客

问题

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:
Assume we are dealing with an environment which could only hold integers within the 32-bit signed integer range. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

第一次解答

class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        negative = x < 0
        if negative:
            x = 0 - x

        if x % 10 == 0:
            x = x // 10

        l = []
        while x:
            l.append(x % 10)
            x = x // 10

        number = 0
        count = 0
        for i in l[::-1]:
            number += (10**count) * i
            count += 1

        if negative:
            return 0 - number
        else:
            return number

结果给我报错了

error_picture

后来突然反应过来，原来将它倒过来之后，也是可能会溢出的，于是改之

Solution

class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        negative = x < 0
        if negative:
            x = 0 - x

        if x % 10 == 0:
            x = x // 10

        l = []
        while x:
            l.append(x % 10)
            x = x // 10

        number = 0
        count = 0
        for i in l[::-1]:
            number += (10**count) * i
            count += 1

        if number > 2**31 - 1:
            return 0
        else:
            if negative:
                return 0 - number
            else:
                return number