Check if connect 4 occurs in matrix

Could someone help me with a code to check if there is a Connect 4 in the following matrix:

0 0 0 0 0 0 0 0 = empty

0 0 2 1 2 2 0 1 = green

1 2 2 2 1 1 2 2 = blue

2 1 1 1 2 1 1

2 1 2 1 2 2 2

1 2 1 2 1 2 1

A Connect 4 occurs when (in this case) 4 of the same color (in this case 1 and 2) line up horizontally, vertically or diagonally.

All help is greatly appreciated!

[The Legend]

I have no clue how to do this myself at the moment.

Answer 1

[Stephen23]

Simple, efficient, and robust using conv2:

>> M = [0,0,0,0,0,0,0;0,0,2,1,2,2,0;1,2,2,2,1,1,2;2,1,1,1,2,1,1;2,1,2,1,2,2,2;1,2,1,2,1,2,1]
M =
   0   0   0   0   0   0   0
   0   0   2   1   2   2   0
   1   2   2   2   1   1   2
   2   1   1   1   2   1   1
   2   1   2   1   2   2   2
   1   2   1   2   1   2   1
>> F = @(x)conv2(x,eye(4),'same')>=4 | conv2(x,flipud(eye(4)),'same')>=4 | conv2(x,ones(4,1),'same')>=4 | conv2(x,ones(1,4),'same')>=4;
>> X1 = F(M==1)
X1 =
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
>> X2 = F(M==2)
X2 =
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
  0  0  0  1  0  0  0
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0
  0  0  0  0  0  0  0

"How would I go about outputting which team won aswell?"

>> C = {'no team','team one','team two','both teams'};
>> X = 1+any(X1(:))+2*any(X2(:));
>> fprintf('%s won!\n',C{X})
team two won!

[The Legend]

This function does not work for diagonal line ups I just noticed..

[Stephen23]

"This function does not work for diagonal line ups I just noticed.."

It does work for diagonals (e.g. your original example matrix, which contains only one line-up (which is diagonal)), but I forgot the anti-diagonal direction. See my updated answer for the simple change to include the anti-diagonal direction.

If you have any examples that do not work with my updated answer then please show them, otherwise I do not have the chance to fix or improve my answer.

Answer 2

[Adam Danz]

It's a little tricky to find a vector within a matrix when the dimensions of the matrix are all larger than the vector. I'm converting the values to characters and using regular expressions to do the matching but there may be a better way.

In any case, here's a demo. See inline comments for details.

% The input matrix 
data = [
    0	0	0	0	0	0	0
    0	0	2	1	2	2	0
    1	2	2	2	1	1	2
    2	1	1	1	2	1	1
    2	1	2	1	2	2	2
    1	2	1	2	1	2	1];

% defined minimum consecutive values (ie, cx=4 equals "connect 4")
cx = 4;
% Define the value to check
checkVal = 2;


% The following checkxxx are all logicals (1/0) where a 1 means a connection is found
checkRows = any(~cellfun(@isempty,regexp(cellstr(char(data)),char(checkVal*ones(1,cx)))));
checkCols = any(~cellfun(@isempty,regexp(cellstr(char(data).'),char(checkVal*ones(1,cx)))));
dataDiags = spdiags(data); % a list of all diagonals
checkDiags = any(~cellfun(@isempty,regexp(cellstr(char(dataDiags).'),char(checkVal*ones(1,cx)))));

% output a final logical 1/0 that indicates a connection was found. 
connectionFound = any([checkRows,checkCols,checkDiags]);

This could easily be put into a loop to find connections for any non-0 element.

unqVals = unique(data(data>0)); 
for i = 1:numel(unqVals)
    checkVal = unqVals(i); 
    . . .
end

[The Legend]

Thank you man, Ill take a close look to what you've done!

[The Legend]

How would I go about outputting which team won aswell? So if the connect 4 is caused by a piece of green (1 as output) or blue (2 as output).

[The Legend]

Do you know how to output the winning team?

[Adam Danz]

" how to output the winning team"

"checkVal" determines which group to test, 1 or 2. You can run it on both groups and output the group that wins. But see Stephen's updated answer since it's simpler.