> For the complete documentation index, see [llms.txt](https://shuati.gitbook.io/crack-lintcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://shuati.gitbook.io/crack-lintcode/linkedin/reverse-integer.md).

# 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.

注意越界

时间 o(n), space o(1)

```java
class Solution {
    public int reverse(int x) {
        long res = 0;
        
        while( x!= 0){
            res = res *10 + x %10;
            x /= 10;
            
            if(res > Integer.MAX_VALUE || res < Integer.MIN_VALUE) return 0;
        }
        
        return (int)res;
    }
}
```

犯错，res应该是long，同时check 是不是比int最大值 最小值大