{leetcode}/problems/count-special-integers/[LeetCode - 2376. Count Special Integers ^]
We call a positive integer special if all of its digits are distinct.
Given a positive integer n, return _the number of special integers that belong to the interval _`[1, n]`.
Example 1:
Input: n = 20 Output: 19 Explanation: All the integers from 1 to 20, except 11, are special. Thus, there are 19 special integers.
Example 2:
Input: n = 5 Output: 5 Explanation: All the integers from 1 to 5 are special.
Example 3:
Input: n = 135 Output: 110 Explanation: There are 110 integers from 1 to 135 that are special. Some of the integers that are not special are: 22, 114, and 131.
Constraints:
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1 ⇐ n ⇐ 2 * 109