# 0788. Rotated Digits

<https://leetcode.com/problems/rotated-digits>

## Description

An integer `x` is a **good** if after rotating each digit individually by 180 degrees, we get a valid number that is different from `x`. Each digit must be rotated - we cannot choose to leave it alone.

A number is valid if each digit remains a digit after rotation. For example:

* `0`, `1`, and `8` rotate to themselves,
* `2` and `5` rotate to each other (in this case they are rotated in a different direction, in other words, `2` or `5` gets mirrored),
* `6` and `9` rotate to each other, and
* the rest of the numbers do not rotate to any other number and become invalid.

Given an integer `n`, return *the number of **good** integers in the range* `[1, n]`.

**Example 1:**

```
**Input:** n = 10
**Output:** 4
**Explanation:** There are four good numbers in the range [1, 10] : 2, 5, 6, 9.
Note that 1 and 10 are not good numbers, since they remain unchanged after rotating.
```

**Example 2:**

```
**Input:** n = 1
**Output:** 0
```

**Example 3:**

```
**Input:** n = 2
**Output:** 1
```

**Constraints:**

* `1 <= n <= 104`

## ac

```java
```