[leetcode] No 7. Reverse Integer python

[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).

 

[Solution]

It is quite simple problem. just reverse digits like [123 > -123]

In my case, I think int such as string.

 

So, int is converted to str using such as str(int).

There are two cases like positive and negative. I just check it in the first element.

 

After submitting, I found that there was a missing case that was reverse integer been smaller than 2^(-31) or larger than 2^31-1. As a result, I added the same code in the first line to the last line.

 

Finally, I passed! 

class Solution:     def reverse(self, x: int) -> int:         if x < -(2**31) or x > (2**31 - 1): return 0                  str_x = str(x)                  first_bit = 0         start_num = 0         num_str = len(str_x)                  if str_x[0] == '-':             first_bit = 1             start_num = 1                  ans = ''                  for i in range(num_str-1, start_num-1, -1):             ans = ans + str_x[i]                  if first_bit == 1:             ans = '-' + ans                  ans = int(ans)                  if ans < -(2**31) or ans > (2**31 - 1): return 0                  return ans