🔥✅✅ Dart Solution 📌📌 || with Explanation 👌👌
Solution
Numbers that produce concatenated results with incorrect lengths (either too short or too long)
Numbers that contain zeros in any of n, 2n, or 3n
Numbe
# Solution

- Numbers that produce concatenated results with incorrect lengths (either too short or too long)
- Numbers that contain zeros in any of n, 2n, or 3n
- Numbers that have duplicate digits in the concatenated result
- Numbers that don't cover all digits from 1-9

### Time Complexity:

**Overall Time Complexity**: O(1) - All operations are constant time since the input size is fixed (n is always a 3-digit number and the concatenated result is at most 9 digits).

```dart
class Solution {
  bool isFascinating(int n) {
    String concatenated = '$n${2 * n}${3 * n}';
    if (concatenated.length != 9) {
        return false;
    }
    if (concatenated.contains('0')) {
        return false;
    }
    Set<String> digits = {};
    for (int i = 0; i < concatenated.length; i++) {
        String digit = concatenated[i];
        if (digits.contains(digit)) {
            return false;
        }
        digits.add(digit);
    }
    return digits.length == 9;
    }
}
```
['Dart']