Class Tree  

Description 
Description =========== A board is an NxM grid. There are NxM tiles. Each space must contain exactly one tile. Tiles are square and each edge has a colour. Tiles can be placed in any one of the four rotations. The task is to place the tiles so that every edge of every tile has is the same colour as the edge it is adjacent to. Input  A number of tile facts, each giving a number (a range of consecutive, ascending integers, starting at 1) that identifies the tile. A number of colour facts (strings, starting with "red", "green", "blue") giving the names of the colours. A number of row facts (consecutive, ascending integers, starting at 1) that identifies the rows of the grid and a similar set of col facts giving the columns. Four rotation facts, giving the possible rotations of each tile in the finished grid. These are 0,90,180 and 360. Four side facts, giving the names of the four sides of each tile. These are "top", "right", "bottom" and "left". A number of tileEdge facts, each giving a tile number, a side and a colour. For example: tile(1). tile(2). tile(3). tile(4). colour(red). colour(green). colour(blue). colour(black). row(1). row(2). col(1). col(2). rotation(0). rotation(90). rotation(180). rotation(270). side(top). side(right). side(bottom). side(left). tileSide(1,top,red). tileSide(1,right,green). tileSide(1,bottom,black). tileSide(1,left,black). tileSide(2,top,blue). tileSide(2,right,red). tileSide(2,bottom,black). tileSide(2,left,black). tileSide(3,top,green). tileSide(3,right,red). tileSide(3,bottom,black). tileSide(3,left,black). tileSide(4,top,red). tileSide(4,right,blue). tileSide(4,bottom,black). tileSide(4,left,black). Output  The input facts plus a chosenPosition and a chosenRotation fact for each tile, giving the (X,Y) location of the tile and the rotation respectively. For example, continuing the previous example: chosenRotation(1,1,90). chosenRotation(1,2,0). chosenRotation(2,1,180). chosenRotation(2,2,270). chosenTile(1,1,1). chosenTile(1,2,3). chosenTile(2,1,2). chosenTile(2,2,4). Calibration  For a given grid, the number of colours controls the difficulty, too few and it will be too easy as there will be too many solutions, too many and it will be too easy as too many tiles can be infered. Ideally there should be around two candidates for each given pair of edges, i.e. (4 * width * height) / colours^2 =~ 2 . Increasing the size of the grid will increase the difficulty if the colour ratio is fixed. Author: Martin Brain 
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