# 7. Reverse Integer

**<font color=red>难度:Easy<font>**

## 刷题内容
> 原题连接

* https://leetcode.com/problems/reverse-integer/

> 内容描述

```
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.
```

> 思路1
******- 时间复杂度: O(n)******- 空间复杂度: O(1)******

一道easy的题目，依次计算各个位的数。不过要注意超出int的范围。

```cpp
class Solution {
public:
    int reverse(int x) {
        long long val = 0;
        do 
        {
            val = val * 10 + x % 10;
            x /= 10;
        } while (x);

        return (val > INT_MAX || val < INT_MIN) ? 0 : val;
    }
};
```