Leetcode 357 Solution

This article provides solution to leetcode question 357 (count-numbers-with-unique-digits)
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https://leetcode.com/problems/count-numbers-with-unique-digits

Solution

class Solution {
public:
    int countNumbersWithUniqueDigits(int n) {
        int total = 1;
        int curr = 1;

        for (int i = 0; i < n; i++)
        {
            if (i == 0)
                curr = 9;
            else
                curr *= 10 - i;
            total += curr;
        }

        return total;
    }
};