7. Reverse Integer

Reverse digits of an integer.

Example 1:

x = 123, return 321

Example 2:

x = -123, return -321

Note:

The input is assumed to be a 32-bit signed integer. Your function should return 0 when the reversed integer overflows.

Solution:

MAX_INT = str(2 ** 31)


class Solution(object):
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        is_negative = x < 0
        num = str(x).lstrip('+-')[::-1]
        if len(num) == len(MAX_INT) and num > MAX_INT:
            return 0
        return -int(num) if is_negative else int(num)

Related:

• 8. String to Integer (atoi)