BrokenChessboard | Topcoder Archive

Problem Statement

A chessboard consists of alternating black and white squares: every square differs in color from the squares that are adjacent to it vertically and horizontally.

You are given a rectangular board of black and white squares in a String[] board. However, the coloring of the squares might not match the chessboard coloring scheme. Each string in board represents a row of squares of the board, and each character (all either 'B' or 'W') represents a square in that row. Return the minimum number of squares that would need their color swapped for the given board to become a valid chessboard.

Definition

Class:: BrokenChessboard
Method:: minimumFixes
Parameters:: String[]
Returns:: int
Method signature:: int minimumFixes(String[] board)
(be sure your method is public)

Constraints

board will contain between 1 and 50 elements, inclusive.
Each element of board will contain between 1 and 50 characters, inclusive.
Each element of board will be the same length.
Each character of each element of board will be either 'B' or 'W'.

Examples

```
{"BWB",
 "BBW",
 "BWW"}
```
```
Returns: 2
```
There are two ways to fix this board: BWB WBW WBW BWB BWB WBW The result on the left would require changing 2 squares (center-left and bottom-right). The result on the right would mean changing 7 squares, so the former is a better choice.
```
{"WW",
 "WW"}
```
```
Returns: 2
```
Either of the two valid boards we could make would take exactly 2 changes.
```
{"BWB",
 "WBW",
 "BWB"}
```
```
Returns: 0
```
This board is already valid, so no fixes are needed.
```
{"B",
 "W",
 "B",
 "B"}
```
```
Returns: 1
```
The board is not square, but anyways it only needs 1 square changed.

{"BWBBB",
 "WWBBW",
 "BBBBW",
 "WBWBB"}

Returns: 7

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