RepeatFreeSquares | Topcoder Archive

Problem Statement

Consider all squares of integers.

Among them, consider only those that contain no repeated digits in their base-10 representation.

Suppose we order them and number them starting from 0: the square 0 gets the index 0, the square 1 gets the index 1, the square 4 gets the index 2, and so on.

Given the int K, return the value at index K, or -1 if K is not a valid index.

Definition

Class:: RepeatFreeSquares
Method:: index
Parameters:: int
Returns:: long
Method signature:: long index(int K)
(be sure your method is public)

Constraints

K will be between 0 and 10^9, inclusive.

Examples

```
9
```
```
Returns: 81
```
The squares at indices 0 through 9 are 0, 1, 4, 9, 16, 25, 36, 49, 64, and 81.
```
10
```
```
Returns: 169
```
The squares 100, 121 and 144 each contain a repeated digit (0, 1, and 4, respectively). The next square in our sequence is therefore 169.
```
47
```
```
Returns: 6084
```

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