• 分類：Math

• 考察知識點：Math

• 最優(yōu)解時間復雜度：**O(n) **

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.

代碼：

我的方法:

class Solution:
    def reverse(self, x):
        if x<-2**31 or x>2**31-1 or x==0:
            return 0
        
        res=0
        s=1
        if x<0:
            s=-1
            x=-x
            
        while x:
            res=(res+(x%10))*10
            print(res)
            x=x//10
            
        res=res//10*s
        if res<-2**31 or res>2**31-1:
            return 0
        return res

討論：

1.簡單哦

Perfect