7. Reverse Integer (python3)

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 store integers within the 32-bit signed integer range: [−2³¹ ,2³¹ − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
code:

class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        str_ = str(abs(x))[::-1]
        i = 0
        while i < len(str_) and str_[i] == '0':
            i += 1
        if x > 0 and int(str_[i:]) < pow(2,31):
            return int(str_[i:])
        elif x  < 0 and int('-'+str_[i:]) >= -pow(2,31):
            return int('-'+str_[i:])
        else:
            return 0

tips:

1.

[::-1]反转string

2.

判断string的元素是否为0的时候，记得用‘0’

3.

仔细看note，如：本例的overflow

4.

输出时，注意转换数据类型