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。
