Integer reversal (Python, LeetCode)

table of Contents

Title description

solution

Code

Code walkthrough

Portal

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Title description

Given a 32-bit signed integer, you need to invert the digits on each bit of the integer. For overflowing 32-bit numbers, 0 is returned.

Input/output description

enter	321
Output	123

 

solution

The topic is relatively simple, and you need to pay attention to two places:

• The number entered may be negative. Negative number is still negative after reversal
• If the inverted number exceeds 32 bits, it needs to return 0

 

Code

class Solution:
    def reverse(self, x: int) -> int:
        positive = True
        if x < 0:
            positive = False
            x = -x

        x = int(str(x)[::-1])
        if not positive:
            x = -x

        if self.out_of_range(x):
            return 0
        else:
            return x

    @staticmethod
    def out_of_range(x: int) -> bool:
        return x > 2 ** 31 - 1 or x < -2 ** 31

 

Code walkthrough

class Solution: 
    def reverse(self, x: int) -> int: # First judge the positive and negative of x. After recording, convert x into a positive number (convenient for reverse order) 
        positive = True 
        if x <0: 
            positive = False 
            x = -x # reverse order, and then restore x 
        x = int(str(x)[: :-1]) 
        if not positive: 
            x = -x # Determine if x overflows 32 bits 
        if self.out_of_range(x): 
            return 0 
        else: 
            return x 
    @staticmethod 
    def out_of_range(x: int) -> bool: 
        return x> 2 ** 31-1 or x <-2 ** 31
        

        

        

 

Portal

LeetCode test question link

str() function

int() function