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 给定一个非负整数…

public class Solution { public int CountNumbersWithUniqueDigits(int n) { ) { ; } ; ; ; && availableNumber > ) { uniqueDigits = uniqueDigits * availableNumber; res += uniqueDigits; availableNumber--; } return res; } } https://leetcode.com/proble…