{leetcode}/problems/count-numbers-with-unique-digits/[LeetCode - Count Numbers with Unique Digits^]
Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n.
Example:
Input: 2
Output: 91
Explanation: The answer should be the total numbers in the range of 0 ≤ x < 100,
excluding 11,22,33,44,55,66,77,88,99
link:{sourcedir}/_0357_CountNumbersWithUniqueDigits.java[role=include]