> For the complete documentation index, see [llms.txt](https://lfool.gitbook.io/leetcodenote/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lfool.gitbook.io/leetcodenote/algorithms/7.-reverse-integer.md).

# 7. Reverse Integer

## Description

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: \[ $$-2^{31}, 2^{31} -1$$]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.

## code

```java
class Solution {
    public int reverse(int x) {
        int res = 0;

        while (x != 0) {
            int tail = x % 10;
            int newNum = res * 10 + tail;
            if ((newNum - tail) / 10 != res) {
                return 0;
            }
            res = newNum;

            x /= 10;
        }
        return res;
    }
}
```