LeetCode： Reverse digits of an integer.

最新推荐文章于 2020-04-03 19:55:33 发布

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#leetcode #Reverse integer

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博客围绕整数反转问题展开，给出示例，如123反转成321，-123反转成-321。同时提出编码前需思考的问题，像整数末位为0时的输出，以及反转后整数可能溢出的情况，并探讨了溢出时的处理办法，如抛异常或重新设计函数。

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题目描述

Reverse digits of an integer.

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

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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).

public class Solution {
    public int reverse(int x) {
        boolean flag=false;
        if(x<0)  //判断是否是负数，如果是负数进行标记
        {
            x=x*(-1);
            flag=true;
        }
        int num=0;
        while(x!=0)
        {
          num=num*10+x%10;
          x=x/10;
        }
        if(flag==true)//负数的话，num最后需要乘以-1
        {
            return num*(-1);
        }else
            return num;
        
        
    }
}