BearPair | Topcoder Archive

Problem Statement

Bear Limak loves algorithms, especially the ones with words and strings.

Limak's friend recently entered a programming competition and wrote a program. The program contains a string constant s. Limak would now like to challenge the program by making it exceed the time limit. To do that, he must find two different characters in s that are as far apart as possible.

Formally, Limak must find two integers i and j with the following properties:

Both i and j must be valid indices into s. That is, both numbers must be between 0 and n-1, inclusive, where n is the length of s.
The characters s[i] and s[j] must be different.
The difference between i and j must be as large as possible.

You are given the String s. If Limak cannot choose any integers with the required properties, return -1. Otherwise, return the largest possible difference between i and j.

Definition

Class:: BearPair
Method:: bigDistance
Parameters:: String
Returns:: int
Method signature:: int bigDistance(String s)
(be sure your method is public)

Constraints

s will have between 2 and 50 characters, inclusive.
Each character in s will be a lowercase English letter ('a' - 'z').

Examples

```
"bear"
```
```
Returns: 3
```
Limak can choose the (0-based) indices 0 and 3. We have s[0]='b' and s[3]='r', which are indeed two different letters. The difference between the two indices is 3-0 = 3.
```
"abcba"
```
```
Returns: 3
```
Here, one optimal solution is for Limak to choose the indices 1 and 4 (corresponding to 'b' and 'a', respectively). Another optimal solution is to choose indices 0 and 3 (letters 'a' and 'b'). In both cases the difference is 3.
```
"oooohyeahpotato"
```
```
Returns: 13
```
```
"zzzzzzzzzzzzzzzzzzzzz"
```
```
Returns: -1
```
Here, Limak can't choose two indices with different letters.
```
"qw"
```
```
Returns: 1
```

"xxyyxyxyyyyyyxxxyxyxxxyxyxyyyyyxxxxxxyyyyyyyyxxxxx"

Returns: 47

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