【Week 9-1】LeetCode 7. Reverse Integer

1.题目：

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.

2.解析:

题目的意思是实现整数的逆序，在Python中实现逆序用切片是一种便捷方式，但是切片可以使用的对象是列表，元祖，字符串，并不包括整数，这时可以考虑把整数转换成字符串，然后再把字符串转换成整数；

3.代码:

class Solution(object):
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        flag = 1 if x >= 0 else -1
        new_x, x = 0, abs(x)
        while x:
            new_x = 10 * new_x + x % 10
            x /= 10
        new_x = flag * new_x
        return new_x if new_x < 2147483648 and new_x >= -2147483648 else 0

4.相关参考:

切片的相关知识>

http://blog.sina.com.cn/s/blog_7e4ac8b501014jki.html

http://blog.youkuaiyun.com/syylx/article/details/44902045