【LeetCode & 剑指offer刷题】字符串题4：Reverse Integer

【LeetCode & 剑指offer 刷题笔记】目录（持续更新中...）

Reverse Integer

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.

---

C++

 

#include<climits>

/*static int x = []() {

    std::ios::sync_with_stdio(false);

    cin.tie(NULL); 

    return 0;

}();*/

class Solution

{

public:

    int reverse(int x)

    {

        //int反转后最大也不超过用33位（1000……）。

        long long res = 0;//保证即使在32位系统中变量也为64位，比int位宽大

        long long t = x; //中间变量

       

        t = t>0? t:-t; //取绝对值

        while(t>0)

        {

            res = res*10 + t%10;

            t /= 10; //t除以10再模10就能依次获得各位数字

        }

       

        //判断符号

        if(x>0)//处理溢出情况

        {

            if(res>INT_MAX) return 0;

            else return res;

        }

        else

        {

            res = -res;

            if(res<INT_MIN) return 0;

            else return res;

        }

       

    }

};