Rotated digits

/*
 * 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
 */
impl Solution {
  pub fn rotated_digits(n: i32) -> i32 {
    let valid = [true, true, true, false, false, true, true, false, true, true];
    let changes = [false, false, true, false, false, true, true, false, false, true];
    (1..=n).filter(|&x| {
      let mut ok = true;
      let mut diff = false;
      let mut num = x;
      while num > 0 {
        let d = (num % 10) as usize;
        if !valid[d] { ok = false; break; }
        if changes[d] { diff = true; }
        num /= 10;
      }
      ok && diff
    }).count() as i32
  }
}