9/4 每日一題(反轉整數)

 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

class Solution:

    def reverse(self, x: int) -> int:

        if x==0:

            return 0

        str_x=str(x)

        if str_x[-1]=='0':

            str_x=str_x[:-1]

        print(f'str_x={str_x}')

        if '-' in str_x:      

            rev = str_x[-1:0:-1]

            print(f'rev={rev}')

            x=int(rev)*-1

            if -2**31 <=x < 2**31 :

                return x

            else:

                return 0

       

        rev=str_x[::-1]

        print(f'rev={rev}')

        x=int(rev)

        if -2**31 <= x < 2**31:

            return x

        else:

            return 0

------------------------------

class Solution:
    def reverse(self, x: int) -> int:
        if x == 0:
            return 0
        isNegative = x < 0
        if isNegative:
            x *= -1
        digits = []
        length = 0
        while (x != 0):
            digits.append(x % 10)
            x = x // 10
            length += 1

        res = 0
        for i in range(length):
            res += 10**(length - i - 1) * digits[i]

        if isNegative:
            res *= (-1)
            if res < (-2)**31:
                return 0
            else:
                return res

        if res > (2)**31 + 1:
            return 0
        else:
            return res