Leetcode 7. Reverse Integer

整型反转，Python 3 实现：

源代码已上传 Github，持续更新。

"""
7. Reverse Integer

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.
"""


"""
7. Reverse Integer

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.
"""

class Solution:

    # 方法一：先转换为字符串
    def reverse_str(self, x):
        """
        :type x: int
        :rtype: int
        """
        result = int(str(x)[::-1]) if x >= 0 else int('-'+str(x)[:0:-1])

        # 32 位 int 类型的范围，第一位为符号位
        return result if result in range(- 2 ** 31, 2 ** 31 -1) else 0

    # 方法二：不转换为字符串
    def reverse(self, x):
        symbol = 1 if x >= 0 else -1
        x *= symbol

        result = 0
        while x > 0:
            result = result * 10 + x % 10
            x = x // 10

        result *= symbol
        return result if result in range(- 2 ** 31, 2 ** 31 - 1) else 0


if __name__ == '__main__':
    solution = Solution()
    print(solution.reverse(-123))

源代码已上传至 Github，持续更新中。