GirlsAndBoys | Topcoder Archive

Problem Statement

There are N students standing in a single row, one next to the other, numbered 0 to N-1 from left to right. Your goal is to minimize the number of adjacent pairs where one student is a boy and the other is a girl. More precisely, you want to minimize the number of values i, 0 <= i < N-1, where student i and student i+1 are of different genders.

You are given the current arrangement as a String row, where the i-th character is 'G' if student i is a girl, and 'B' if student i is a boy. In a single move, you can choose two adjacent students and swap their positions. Return the minimum number of moves required to achieve your goal.

Definition

Class:: GirlsAndBoys
Method:: sortThem
Parameters:: String
Returns:: int
Method signature:: int sortThem(String row)
(be sure your method is public)

Constraints

row will contain between 1 and 50 characters, inclusive.
Each character in row will be 'G' or 'B'.

Examples

```
"GGBBG"
```
```
Returns: 2
```
You can swap the rightmost girl with the two boys (one after the other) to get "GGGBB", with a minimum of only 1 pair of adjacent students of different gender.
```
"BBBBGGGG"
```
```
Returns: 0
```
There is already a single pair of adjacent students of different gender, and there is no arrangement without such pairs at all, so the best solution is to swap nothing.
```
"BGBGBGBGGGBBGBGBGG"
```
```
Returns: 33
```
```
"B"
```
```
Returns: 0
```
With only one student, there is not much swapping to do.

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