WhiteHats | Topcoder Archive

Problem Statement

There is a number of people in a room, and each of them wears a hat which is either black or white. Every person counts the number of other people wearing white hats. You are given a int[] count, the i-th element of which is the number counted by the i-th person. Return the total number of people wearing white hats, or -1 if count doesn't correspond to a valid situation.

Definition

Class:: WhiteHats
Method:: whiteNumber
Parameters:: int[]
Returns:: int
Method signature:: int whiteNumber(int[] count)
(be sure your method is public)

Constraints

count will contain between 2 and 50 elements, inclusive.
Each element of count will be between 0 and 50, inclusive.

Examples

```
{2,1,1}
```
```
Returns: 2
```
The first person wears a black hat and sees two people wearing white hats. Each person wearing a white hat sees only one other white hat in the room.
```
{2,2,2}
```
```
Returns: 3
```
Everyone wears a white hat here.
```
{0,0}
```
```
Returns: 0
```
Black hats only.
```
{1,1,1,2}
```
```
Returns: -1
```
```
{10,10}
```
```
Returns: -1
```
Now that's interesting. There are only two people in the room, yet each of them counted 10 others.

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