# Solving Leetcode Interviews in Seconds with AI: Check if The Number is Fascinating


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "2729" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like [Chatmagic](https://www.chatmagic.app), we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

	# Problem Statement
	> You are given an integer n that consists of exactly 3 digits. We call the number n fascinating if, after the following modification, the resulting number contains all the digits from 1 to 9 exactly once and does not contain any 0's:  Concatenate n with the numbers 2 * n and 3 * n.  Return true if n is fascinating, or false otherwise. Concatenating two numbers means joining them together. For example, the concatenation of 121 and 371 is 121371.   Example 1:  Input: n = 192 Output: true Explanation: We concatenate the numbers n = 192 and 2 * n = 384 and 3 * n = 576. The resulting number is 192384576. This number contains all the digits from 1 to 9 exactly once.  Example 2:  Input: n = 100 Output: false Explanation: We concatenate the numbers n = 100 and 2 * n = 200 and 3 * n = 300. The resulting number is 100200300. This number does not satisfy any of the conditions.    Constraints:  100 <= n <= 999  

	# Explanation
	Here's a solution to determine if a 3-digit number is fascinating, along with an explanation of the approach and complexity analysis.

*   **Concatenate and Convert:** Calculate `2*n` and `3*n`, concatenate `n`, `2*n`, and `3*n` into a single string.
*   **Digit Frequency Check:** Check if the concatenated string's length is 9 and if it contains unique digits from '1' to '9'.
*   **Boolean Return:** Return `True` if the above conditions are met; otherwise, return `False`.

*   **Time Complexity:** O(1), **Space Complexity:** O(1) - The operations are performed on a fixed number of digits and constant-size data structures.

	
	# Code
	```python
	def is_fascinating(n: int) -> bool:
    """
    Determines if a 3-digit number n is fascinating.

    A number n is fascinating if concatenating n, 2*n, and 3*n contains
    all digits from 1 to 9 exactly once and no 0s.

    Args:
        n: A 3-digit integer.

    Returns:
        True if n is fascinating, False otherwise.
    """

    s = str(n) + str(2 * n) + str(3 * n)
    if len(s) != 9:
        return False

    digits = set(s)
    if len(digits) != 9:
        return False

    for digit in digits:
        if digit == '0':
            return False

    for i in range(1, 10):
        if str(i) not in s:
            return False

    return True
	```