# Leetcode 筆記 :(7) Reverse Integer
###### tags: `Leetcode`
## 題目
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

Example 4:

Input: x = 0
Output: 0

Constraints:

``-231 <= x <= 231 - 1``
## 思考方向
1. 第一個思考則是直接使用Python 的Str處理
2. 第二則是跟其他語言一樣使用mod運算去處理
## Code

### Solution 1(str)

class Solution:
    def reverse(self, x: int) -> int:
        minus = False
        
        if x < 0:
            minus = True
            x = abs(x)
            
        result = str(x)[::-1]        
        result = int(result)
        
        if minus == True:
            result = -1*result
        
                
        if result > 2**31 or result < -2**31:
            return 0
        else:
            return result

### Solution 2(Mod)

class Solution:
    def reverse(self, x: int) -> int:

        minus = False
        result = ''
        if x < 0:
            minus = True
            x = abs(x)

        if x ==0:
            result = '0'

        while(x != 0):            
            tmp = int(x%10)
            x = (x-tmp)/10
            tmp = str(tmp)
            result += tmp
        
        result = int(result)
            
        if minus == True:          
            result = -1*result
            
        if result > 2**31 or result < -2**31:
            return 0 
        
        else:  
        
            return result