UniqueDigits

Problem statement, definition, constraints, and public examples.

Problem Statement

Given an int n find all positive integers less than n whose digits are all different. Return the total number of such integers.

Definition

Class:: UniqueDigits
Method:: count
Parameters:: int
Returns:: int
Method signature:: int count(int n)
(be sure your method is public)

Constraints

n will be between 1 and 10000 inclusive.

Examples

```
21
```
```
Returns: 19
```
We count all integers between 1 and 20, except 11.
```
101
```
```
Returns: 90
```
```
1001
```
```
Returns: 738
```
```
1
```
```
Returns: 0
```

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