leetcode

0 class Solution {

1 public:

2 int countNumbersWithUniqueDigits(const int n) const {

3 if (n == 0) return 1;

4

5 int res = 10, acc = 9, crnt = 9;

6 for (int i = 2; i <= n; i++)

7 res += acc *= crnt--;

8

9 return res;

10 }

11 };