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Count Numbers with Unique Digits
medium
Description
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Solution
Test Cases
Test Result
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Count Numbers with
Unique Digits
Given an integer n, count how many numbers with unique digits exist between 0 and 10^n - 1.
Examples
Example 1
Input:
0
Output:
1
Example 2
Input:
1
Output:
10
Hints
Hint 1
For n=0, only number 0 exists → 1
Hint 2
For n=1, digits 0-9 → 10
Hint 3
For n>1, use multiplication: first digit has 9 options (not 0), subsequent have decreasing options
Related Problems
24-game
additive-number
all-paths-from-source-to-target
Count Numbers with Unique Digits
Given an integer n, count how many numbers with unique digits exist between 0 and 10^n - 1.