7-Reverse-Integer.md

7. Reverse Integer

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

Note:

Assume we are dealing with an environment that 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.

Example 1:

Input: x = 123
Output: 321

Example 2:

Input: x = -123
Output: -321

Example 3:

Input: x = 120
Output: 21

Example 4:

Input: x = 0
Output: 0

Constraints:

• -231 <= x <= 231 - 1

Solution

class Solution:
    def reverse(self, x: int) -> int:
        ans = int(str(x)[::-1]) if x >= 0 else (-1) * int(str(x)[-1:0:-1])
        return ans if -2**31 <= ans < 2**31 else 0

Python 3's convenient string operation.