grade(A,movesCtr,mv)

function [score,A] = grade(A,movesCtr,mv)
%GRADE Make sure the answer is valid and compute its score.

% Copyright 2006 The MathWorks, Inc.

% N=1, E=2, S=3, W=4
I = [-1  0  1  0 ];
J = [ 0  1  0 -1 ];
N = false(size(A));

% Check maximum number of moves allowed
if size(mv,1)>movesCtr || size(mv,2)~=3
    error('Too many rows (more than NMOVES).')
end

% First (second) column of moves should be integer values from 1 to
% num_rows (num_columns)
if ~all(ismember(mv(:,1),1:size(A,1))) || ~all(ismember(mv(:,2),1:size(A,2)))
    error('Indices are outside the bounds of the board.');
end

% Third column of moves should be integer values from 0 to 4
if ~all(ismember(mv(:,3),0:4))
    error('Third column must have only integer values from 0 to 4');
end

for k = 1:size(mv,1) % for every move
    cp = mv(k,1:2);
    if A(cp(1),cp(2))>0 %current block must be a non-empty space
        if mv(k,3) % swap ?
            np = cp + [I(mv(k,3)) J(mv(k,3))];
            % swap block must be within the bounds of the board and a non-empty space
            if all(np>=1) && all(np<=size(A))  &&   A(np(1),np(2))>0
                A([cp(1),np(1)],[cp(2),np(2)]) = A([np(1),cp(1)],[np(2),cp(2)]);
            else
                warning('Swap to an empty space or beyond the bounds of the board.')
            end
        else % remove block and neighbors
            N(:) = false;
            findNeighbors(cp(1),cp(2),A(cp(1),cp(2)));
            if sum(N(:))>1
                anyN = any(N);
                for j = 1:size(A,2)
                    if anyN(j)
                        tmp = A(~N(:,j),j);
                        A(:,j) = 0;
                        A(end-sum(~N(:,j))+1:end,j) = tmp;
                    end
                end
            else
               warning('You cannot pop single blocks.')
            end
        end
    else
        warning('Indices point to an empty space.')
    end
end
score = sum(A(:));

    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    function findNeighbors(i,j,c)
        if ~N(i,j);
            N(i,j) = true;
            if i>1         && A(i-1,j)==c; findNeighbors(i-1,j,c); end
            if j<size(A,2) && A(i,j+1)==c; findNeighbors(i,j+1,c); end
            if i<size(A,1) && A(i+1,j)==c; findNeighbors(i+1,j,c); end
            if j>1         && A(i,j-1)==c; findNeighbors(i,j-1,c); end
        end
    end % end of findNeighbors (nested function)
end % end of grade (subfunction)