LeetCode 7. Reverse Integer

Given a 32-bit signed integer, reverse digits of an integer.

Example 1:

Input: 123
Output: 321

Example 2:

Input: -123
Output: -321

Example 3:

Input: 120
Output: 21

Note:

Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

这个题就是给一个整数，将这个整数倒置，有一个边界检测。

刚开始我是直接暴力导致，每个数算出每一位，然后倒着输出，做的时候要注意区分整数和负数。

class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        ret=0
        flag=0
        if x<0:
            x=-x
            flag=1
        while(x):
            a=x%10
            ret=ret*10+a
            x//=10
        if ret>2**31-1 or ret<-2**31:
            return 0
        if flag==1:
            return -ret
        else:
            return ret

然后我又看了看大佬的做法，是用切片，好简单。Beat 99.97%

class Solution:
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        if x<0:
            ret=-1*int(str(-x)[::-1])
        else:
            ret=int(str(x)[::-1])
        if ret<-2**31 or ret>2**31-1:
            return 0
        else:
            return ret