動機
要自己處理32位整數的溢位
Problem
Given a signed 32-bit integer x
, return x
with its digits reversed. If reversing x
causes the value to go outside the signed 32-bit integer range [-231, 231 - 1]
, then return 0
.
Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
Example 1:
Input: x = 123Output: 321
Example 2:
Input: x = -123Output: -321
Example 3:
Input: x = 120Output: 21
Example 4:
Input: x = 0Output: 0
Constraints:
-231 <= x <= 231 - 1
Sol
class Solution:
def reverse(self, x: int) -> int:
ret,minus,x,cons = 0,(x<0),abs(x),2**31
while x != 0:
ret += (x%10)
ret, x = ret*10, x//10
ret = ret//10
ret = -ret if minus else ret
return ret if -cons <= ret <= cons-1 else 0