7-reverse-integer

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Description

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).

 

Example 1:

Input: x = 123
Output: 321

Example 2:

Input: x = -123
Output: -321

Example 3:

Input: x = 120
Output: 21

 

Constraints:

• -231 <= x <= 231 - 1

Solution(Python)

class Solution:
    def __init__(self):
        self.LOW = -(2**31)
        self.HIGH = 2**31

    def reverse(self, x: int) -> int:
        rev = 0
        isNeg = x < 0
        if isNeg:
            x *= -1
        while x != 0:
            pop = x % 10
            x //= 10

            if (rev >= self.HIGH // 10 or rev >= self.HIGH) and pop > 7:
                return 0
            if (rev <= self.LOW // 10 or rev <= self.LOW) and pop < -8:
                return 0

            rev = rev * 10 + pop
        if isNeg:
            rev *= -1
        if self.LOW < rev < self.HIGH:
            return rev
        else:
            return 0