THIS PROBLEM WAS TAKEN FROM THE SEMIFINALS OF THE TOPCODER INVITATIONAL
TOURNAMENT
Class Name: Tothello
Method Name: bestMove
Parameters: String[], String[], String
Returns: int
Method signature (be sure your method is public): int bestMove(String[]
redPieces, String[] blackPieces, String whoseTurn);
PROBLEM STATEMENT
The game Tothello is a TopCoder modified version of the board game Othello.
The game is played on an 8 x 8 grid with two players, Black and Red. The
players alternate turns placing one piece representing their color in one empty
square of the grid. When the Red player puts a red piece down, any black
pieces that end up between the piece that was placed on the board and any other
red piece already on the board should be changed to red. If the change in
color from black to red of any piece on the board causes other black pieces to
lie between two red pieces, those black pieces should also be changed to red.
The changing of black pieces will continue until no one black piece lies
between two red pieces. The manner that pieces change color apply when the
Black player places a piece on the grid, however, the pieces would then change
from red to black. A player also has the option of passing - not putting any
pieces down - on his turn, in which case the other player just gets to go twice
in a row.
You are to write a program that helps a player determine their best possible
move - the move that results in the most pieces being that player's color at
the end of the move.
Implement a class Tothello that contains a method bestMove. bestMove inputs
the current state of the grid before a specified player's move and outputs the
number of the player's pieces on the board as a result of the player's best
move.
NOTES
- redPieces is a String[] representing the current positions of red pieces on
the board.
- blackPieces is a String[] representing the current positions of black pieces
on the board.
- The board is an 8x8 grid with the columns referred to by the uppercase
letters A-H and the rows referred to by the numbers 1-8 (inclusive). The
column is specified before the row. A1 is in the upper left. H8 is in the
lower right.
- redPieces and blackPieces are not necessarily the same length (players may
have passed on moves).
- A black piece is between two red pieces if a red piece can be found before an
empty square on either side by following the horizontal, vertical, or either
diagonal out from the Black piece. For example:
- - - R - - - -
- - - B - - - -
- - - B - - - - All three Black pieces are between two red pieces.
- - - B - - - -
- - - R - - - -
- - - R - - - -
- - - B B - - -
- - - B - B - - All four Black pieces are between two Red pieces.
- - - R R R R R
- - - R - - - -
- - - B R - - -
- - - - - - - - The Black piece is not between two Red pieces.
- - - R R - - -
R R R R R R R R
R - - - - - - R
R - B B - B - R
R - B B B B - R None of the Black pieces are between two Red pieces.
R - - - - - - R
R R R R R R R R
TopCoder will ensure the validity of the inputs. Inputs are valid if all of
the following criteria are met:
- Both redPieces and blackPieces contain between 0 and 50 elements (inclusive).
- All elements of redPieces and blackPieces consist of uppercase letters A-H
and numbers 1-8 (inclusive).
- All elements of redPieces and blackPieces are in the form of letter-number
pairs with each letter representing the column and each number representing the
row of the piece's position (i.e. "A2" where 'A' is the column and '2' is the
row of the piece's position).
- whoseTurn is a String that is equal to either "Red" or "Black" representing
the player for which the method is being run.
- The current state of the board represented by redPieces and blackPieces
contains no red pieces between any black pieces and no black pieces between any
red pieces (a state where there were black pieces between red pieces is
impossible at the start of a move, assuming the game has been played
correctly.)
- The elements are unique in redPieces and blackPieces, and redPieces and
blackPieces do not contain any of the same elements.
- The game board must start with at least one unoccupied space.
EXAMPLES
If redPieces=[C2,C3,C4,C5,D4,E4,F2,F3,F4,F5,G6] and
blackPieces=[B1,E1,G1,C6,H7,G4] and whoseTurn="Black",
Before the player's move, the board is:
A B C D E F G H
1 - B - - B - B -
2 - - R - - R - -
3 - - R - - R - -
4 - - R R R R B -
5 - - R - - R - -
6 - - B - - - R -
7 - - - - - - - B
8 - - - - - - - -
Black's best move is C1, which results in:
A B C D E F G H A B C D E F G H A B C D E F G H A B C D E F
G H
1 - B - - B - B - 1 - B B - B - B - 1 - B B - B - B - 1-BB-B-B-
2 - - R - - R - - 2 - - B - - R - - 2 - - B - - R - - 2 - - B - - R
- -
3 - - R - - R - - 3 - - B - - R - - 3 - - B - - R - - 3 - - B - - R
- -
4 - - R R R R B - --> 4 - - B R R R B - --> 4 - - B B B B B - --> 4 - - B B B B
B -
5 - - R - - R - - 5 - - B - - R - - 5 - - B - - R - - 5 - - B - - B
- -
6 - - B - - - R - 6 - - B - - - R - 6 - - B - - - R - 6 - - B - - -
B -
7 - - - - - - - B 7 - - - - - - - B 7 - - - - - - - B 7 - - - - -
- - B
8 - - - - - - - - 8 - - - - - - - - 8 - - - - - - - - 8 - - - - - -
- -
There end up being 16 black pieces, so the method should return 16.
If redPieces=[A1,B8,C6,C8,D8] and blackPieces=[B2,C2,C3,C4,C5] and
whoseTurn="Red", Red's best move is C1, and the method should return 11.
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