Explanation of the checking algorithm

As you know, the game has a 8x8 matrix with one gem on each square. I had to write an algorithm that checks for horizontal and vertical groups of three or more gems.

Data types

A Coord is an object that stores the coordinates of a square. It's just got the horizontal and vertical position of the square and some methods.

A Match is a set (actually a vector) of three or more adjacent Coords, either horizontally or vertically aligned. It's got a method called matched that looks if a coordinated was matched in that match.

A MultipleMatch is a set of Matches. It's just a plain vector with an additional method called matched that checks if a given coordinate was matched in any of the stored matches.

Algorithm

The checking algorithm returns a MultipleMatch objects with all the found matches. How does it find the matches? Easy.

First, it looks for matching rows (that is, horizontal groups of three or more equal gems). For the first row, it checks every column.

So we're at the first square, x=0, y=0. A temporary Match object is created to store the matching squares. Then, we begin to loop over the squares to the right of the current stage, checking if the gem equals the gem at 0,0. Is it the same? Yes: we add the square to the Match object. No: we break the loop, because now it's impossible to find a consecutive matching group. Also, we jump the column loop to the last read square, because we know that there are no groups so far.

Every Match object with three or more squares is added to the MultipleMatch object that the function will return.

Here's the code for the row checking:

    MultipleMatch matches;    

    for(int y = 0; y < 8; ++y){

	for(int x = 0; x < 8; ++x){

	    Match currentRow;
	    currentRow.push_back(coord(x,y));

	    for(k = x+1; k < 8; ++k){
		if(squares[x][y] == squares[k][y] &&
		   squares[x][y] != sqEmpty){
		    currentRow.push_back(coord(k,y));
		}else{
		    break;
		}
	    }

	    if(currentRow . size() > 2){
		matches.push_back(currentRow);
	    }

	    x = k - 1;
	}	
    }

The very same happens when we check for matching vertical groups.