[LeetCode] Challenge log 7

Posted on |
7. Reverse Integer

Normal question, but be aware of the upper bound and lower bound.

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

1
2
Input: 123
Output: 321

Example 2:

1
2
Input: -123
Output: -321

Example 3:

1
2
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.

Soulution:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        def maxint():
            m = 1
            for i in range(31):
                m = m << 1
            return -m, m-1
        
        s = str(x)
        if s[0] == '-':
            sign = -1
            s = s[1:]
        else:
            sign = +1
        
        lb, ub = maxint()
        # print(lb, ub)
        x = int(s[::-1])
        x = sign * x
        if x < lb or x> ub:
            x = 0
            
        return x
0%