Given an integer n, return the count of all numbers x with unique digits such that $0 \le x < 10^n$.

Constraints:

• $0 \le$ n $\le 8$

Now, let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.