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 Problem Statement for TheTilesDivOne

Problem Statement

    John and Brus have a rectangular chessboard with black and white tiles. Rows and columns of the chessboard are numbered starting from 0. The cell at row i, column j is black if i+j is even and it is white if i+j is odd.

Some of the cells of the chessboard are occupied by chess pieces. You are given a String[] board. For each i and j, the j-th character of the i-th element (0-based indices) of board is 'X' if the cell in row i, column j of the chessboard contains a chess piece. Otherwise, the j-th character of the i-th element of board is '.'.

John and Brus also have an infinite supply of L-shaped tiles. Each tile consists of three squares which are of the same size as the cells of the chessboard. I.e., each tile looks as follows:
John and Brus want to place some of the tiles onto their chessboard, according to the following rules:
  • Each tile may be rotated by any multiple of 90 degrees.
  • Each tile must cover exactly three cells of the chessboard.
  • Tiles are not allowed to overlap.
  • Tiles are not allowed to cover the cells that are already occupied by the chess pieces.
  • The corner cell of each tile must cover a black cell of the chessboard.

Return the maximum number of tiles John and Brus can place on the board according to the above rules.


Method signature:int find(String[] board)
(be sure your method is public)


-board will contain between 1 and 47 elements, inclusive.
-Each element of board will contain between 1 and 47 characters, inclusive.
-All elements of board will contain the same number of characters.
-Each element of board will consist of only characters 'X' and '.'.


Returns: 1
Since only one black cell is available, just one tile can be placed on the board.
Returns: 2
Returns: 0
Returns: 13

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This problem was used for:
       Single Round Match 575 Round 1 - Division I, Level Three