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.
My silly solution:
class Solution:
def reverse(self, x):
"""
:type x: int
:rtype: int
"""
MAX_INT = 2147483647 # 2**31-1
# MIN_INT = -2147483648 # -2**31
s = str(abs(x))
l = []
l += s
l.reverse()
num = int(''.join(l))
if num > MAX_INT:
return 0
if x >= 0:
return num
else:
return -num
kvas's solution(official thinking):
class Solution(object):
def reverse(self, x):
"""
:type x: int
:rtype: int
"""
MAX_INT = 2147483647 # 2**31-1
MIN_INT = -2147483648 # -2**31
rev = 0
sign = (x > 0) - (x < 0)
x = abs(x)
while x != 0:
rev = rev * 10 + x % 10
if rev > MAX_INT or rev < MIN_INT:
return 0
x //= 10
return rev * sign
