python3 integer inversion

python3 integer inversion

Give you a 32-bit signed integer x, and return the result of inverting the digital part of x.

If the integer exceeds the 32-bit signed integer range [−2^31, 2^31 − 1] after the inversion, 0 is returned.

Assume that the environment does not allow storage of 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
Example 4:

Input: x = 0
Output: 0

Idea 1: Convert it to a string, flip it, and judge whether it is positive or negative. Finally, the title requires that if the inverted integer exceeds the range of 32-bit signed integers [−2^31, 2^31 − 1], 0 will be returned

class Solution:
    def reverse(self, x: int) -> int:
        str1 = str(x)
        
        if str1[0] == '-':
            str1 = str1[0] + str1[:0:-1]
        else:
            str1 = str1[::-1]
        return int(str1) if -2147483648<int(str1)<2147483648 else 0

Idea 2: Do not use strings. When the flipped number is greater than the condition, it returns 0

class Solution:
    def reverse(self, x: int) -> int:
		y, res = abs(x), 0
        # 则其数值范围为 [−2^31,  2^31 − 1]
        boundry = (1<<31) -1 if x>0 else 1<<31
        while y != 0:
            res = res*10 +y%10
            if res > boundry :
                return 0
            y //=10
        return res if x >0 else -res

Improve:

class Solution:
    def reverse(self, x: int) -> int:
        str1 = str(x)
        
        if str1[0] == '-':
            str1 = str1[0] + str1[:0:-1]
            a=int(str1)
            if (1<<31)<abs(a):
                return  0
        else:
            str1 = str1[::-1]
            a= int(str1)
            if a>(1<<31) -1:
                return 0
        return a 

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Origin blog.csdn.net/qq_43710889/article/details/115341615