Leetcode 357. Count Numbers with Unique Digits

文章作者：Tyan
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1. Description

Count Numbers with Unique Digits

2. Solution

class Solution {
public:
    int countNumbersWithUniqueDigits(int n) {
        int total = 1;
        for(int i = 0; i < n; i++) {
            int count = 9;
            for(int j = 1; j <= i; j++) {
                count *= (10 - j);
            }
            total += count;
        }
        return total;
    }
};

Reference

1. https://leetcode.com/problems/count-numbers-with-unique-digits/description/