788. Rotated Digits
Medium
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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`
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