7. reverse text

Gives a 32-bit signed integer, you need this integer number on each inverted.

Input: 123 
Output: 321

Input: -123 
Output: -321

Input: 120 
Output: 21

note:

Suppose we have an environment can only store 32-bit signed integer, please Under this assumption, if the reverse integer overflow it returns 0. Values ​​in the range [-2 ^ 31, 2 ^ 31 - 1]

And topics like yesterday, right? However, there are several different places, see the second example, enter 123, the required output -321, indicating that the reversal was not signed.

 There is a special condition that the value range of [-2 ^ 31, 2 ^ 31--1], that is, when the output value is also necessary to determine the size.

# -*-coding utf-8-*-
def reverse(x):
    num = 0
    a = abs(x)
    while a != 0:
        temp = a % 10
        num = num * 10 + temp
        a = a // 10

    if x > 0 and num < (2 ^ 31 - 1):
        return num
    elif x < 0 and num > (-2 ^ 31):
        return -num
    else:
        return 0


rd = reverse(int(-123))
print(rd)