Reverse Interger

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?

Throw an exception? Good, but what if throwing an exception is not an option? You would then have to re-design the function (ie, add an extra parameter).

分析：我们可以从余数和除数方面考虑，我们一般会想到怎么样才能得到给定的数各个位上的数字，我们就可以用除10取余。知道除数为0为止。

class Solution {
public:
    int reverse(int x) {
        int res=0;
        while(x!=0)
        {
            res=res*10+x%10;
            x=x/10;
        }
        return res;
    }
};

python:

class Solution:
    # @return an integer
    def reverse(self, x):
        flag=False
        res=0
        if x<0:
            x=-x
            flag=True
        while x>0:
            res=res*10+x%10
            x=x/10
        if flag:
            res=-res
        return res