LeetCode_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 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.

解题 def reverse(x): """ :type x: int :rtype: int """ y = -x if x < 0 else x list = [] last = y while last > 0: list.append(last % 10) last //= 10 sum = 0 length = len(list) for l in list: length -= 1 sum += l * 10 ** length result = -sum if x < 0 else sum if result > 2147483647 or result < -2147483648: return 0 return result 思路

这里利用了不断对10作除法，所获得的余数顺序正好与原数字相反的特性。