[TOC]

P007 Reverse Integer

Reverse digits of an integer.

Example1: x = 123, return 321
Example2: x = -123, return -321

Have you thought about this?
Here are some good questions to ask before coding. Bonus points for you if you have already thought through this!

If the integer's last digit is 0, what should the output be? ie, cases such as 10, 100.

Did you notice that the reversed integer might overflow? Assume the input is a 32-bit integer, then the reverse of 1000000003 overflows. How should you handle such cases?

For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

思路分析

没必要当做数字处理，使用字符串操作更加简单。

代码

java

public class Solution007 {
    public int reverse(int x) {
        try {
            StringBuilder sb = new StringBuilder(new Integer(x).toString());
            if (x < 0)
                sb.deleteCharAt(0);

            return x < 0 ? -Integer.parseInt(sb.reverse().toString()) : Integer.parseInt(sb.reverse().toString());
        } catch (NumberFormatException e) {
            return 0;
        }
    }
}

python

class Solution007(object):
    def reverse(self, x):
        """
        :type x: int
        :rtype: int
        """
        ret = ""
        if x < 0:ret = "-"
        
        ret += str(abs(x))[::-1]
        return int(ret)