AllEven | Topcoder Archive

Problem Statement

A number is paired up if the number of occurrences of each digit is even. For example, 22, 4242, and 7720707727 are paired up, but 33033 and 12345 are not.

Given the longs lo and hi, count the paired up numbers in the closed interval [lo, hi].

Definition

Class:: AllEven
Method:: countInRange
Parameters:: long, long
Returns:: long
Method signature:: long countInRange(long lo, long hi)
(be sure your method is public)

Constraints

hi will be between 0 and 10^18 - 1, inclusive.
lo will be between 0 and hi, inclusive.

Examples

```
47
```
```
999
```
```
Returns: 5
```
The five numbers are 55, 66, 77, 88, and 99.
```
47
```
```
1010
```
```
Returns: 7
```
Compared to the previous example we now also gained 1001 and 1010.
```
12345678901
```
```
98765432109
```
```
Returns: 0
```
```
1234
```
```
654321
```
```
Returns: 6862
```
```
0
```
```
10
```
```
Returns: 0
```
Note that zero is not a paired up number, as it has an odd number of zeros.

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