# Rotated digits

`x`

is a good number 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. 0, 1, and 8 rotate to themselves; 2 and 5 rotate to each other (on 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.

Now given a positive number `n`

, how many numbers `x`

from `1`

to `n`

are good?

```
Example:
Input: 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.

c++ implementation:

int rotatedDigits(int n) { int c=0; while(n) { int x=n; int f=0; while(x) { int d=x%10; if(d==3 ||d==4||d==7) { f=0; break; } else if(d== 2 || d == 5 || d == 6 || d == 9) { f=1; } x=x/10; } if(f==1) c++; n=n-1; } return c; }