I have been programming Connect 4 using Matlab and im using the minimax algorithm and when I play it it blocks be on on the horizontals, and vertical, but when I can when using diagonals it wont block me at all and I have no reason why. Here is my code.


function [ max ] = maxMove(BoardMax,depthMax,alphaMax,betaMax)
%UNTITLED2 Summary of this function goes here
% Detailed explanation goes here
global bestMove;
max = -inf;
m = checkForWinner(BoardMax);
if(m)
max = m;
elseif(depthMax >= 5)
max = analysis(BoardMax);
else

%find all legal moves
legalMoves = findAllLegalMoves(BoardMax);
sizeOf = size(legalMoves,1);
%loop through all the moves
for i = 1:1:sizeOf
%check for winner
cMax = BoardMax;
if(legalMoves(i,1) == 0)
break;
end
cMax( legalMoves(i,1) , legalMoves(i,2) ) = 2;
temp = minMove(cMax,depthMax + 1,alphaMax,betaMax);
if(temp > max)
max = temp;
if(depthMax == 0)
bestMove = [legalMoves(i,1),legalMoves(i,2)];
end
end
if(temp > alphaMax)
alphaMax = max;
end
if(alphaMax > betaMax)
max = alphaMax;
end
end
end

end




function [ min ] = minMove(BoardMin,depthMin,alphaMin,betaMin)
%UNTITLED3 Summary of this function goes here
% Detailed explanation goes here
global bestMove;min = inf;
m = checkForWinner(BoardMin);
if(m)
min = m;
elseif(depthMin >= 5)
min = analysis(BoardMin);
else

%find all legal moves
legalMoves = findAllLegalMoves(BoardMin);
sizeOf = size(legalMoves,1);
%loop through all the moves
for i = 1:1:sizeOf
cMin = BoardMin;
if(legalMoves(i,1) == 0)
break;
end
cMin(legalMoves(i,1),legalMoves(i,2)) = 1;
temp = maxMove(cMin,depthMin + 1,alphaMin,betaMin);
if(temp < min)
min = temp;
if(depthMin == 0)
bestMove = [legalMoves(i,1),legalMoves(i,2)];
end
end
if(temp < betaMin)
betaMin = min;
end
if(alphaMin > betaMin)
min = betaMin;
end
end
endend



function [winner] = checkForWinner(Board)
global bestMove;
winner = 0;

% check for vertical win

% loop through each column
for j = 1:1:7
% check for four together in that column
for k = 1:1:3
% if four ones are together the human wins
if((Board(k,j) == 1) && (Board(k + 1,j) == 1) && (Board(k+2,j) == 1) && (Board(k+3,j) == 1))
winner = -500000;
%else if four twos are together the computer wins
elseif((Board(k,j) == 2) && (Board(k + 1,j) == 2) && (Board(k+2,j) == 2) && (Board(k+3,j) == 2))
winner = 500000;
end
end
end


% check for horizontal win

%loop through each row
for i = 1:1:6
for k = 1:1:4
if((Board(i,k) == 1) && (Board(i,k + 1) == 1) && (Board(i,k + 2) == 1) && (Board(i,k + 3) == 1))
winner = -500000;
elseif((Board(i,k) == 2) && (Board(i,k + 1) == 2) && (Board(i,k + 2) == 2) && (Board(i,k + 3) == 2))
winner = 500000;
end

end
end

% check for diagonal win left top to right down

for row = 1:1:3
for column = 1:1:4
if((Board(row,column) == 1) && (Board(row + 1,column + 1) == 1) && (Board(row + 2,column + 2) == 1) && (Board(row + 3,column + 3) == 1))
winner = -500000;
elseif((Board(row,column) == 2) && (Board(row + 1,column + 1) == 2) && (Board(row + 2,column + 2) == 2) && (Board(row + 3,column + 3) == 2))
winner = 500000;
end
end
end

%check for diagonal win right top to left down
for row = 1:1:3
for column = 7:-1:4
if((Board(row,column) == 1) && (Board(row + 1,column - 1) == 1) && (Board(row + 2,column - 2) == 1) && (Board(row + 3,column - 3) == 1))
winner = -500000;
elseif((Board(row,column) == 2) && (Board(row + 1,column - 1) == 2) && (Board(row + 2,column - 2) == 2) && (Board(row + 3,column - 3) == 2))
winner = 500000;
end
end
end
end

This still needs coded

function [ whoWon ] = analysis(BoardAnalysis)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
global bestMove;
whoWon = 0;
end



function [ coordinates ] = findAllLegalMoves(Board)
%UNTITLED4 Summary of this function goes here
% Detailed explanation goes here
global bestMove;
numberOfFutureMoves = 0;
coordinates(numberOfFutureMoves + 1,1) = 1;
coordinates(numberOfFutureMoves + 1,2) = 1;
for i = 1:1:7
for j = 1:1:6
row = 0;
if(j == 1)
if(Board(j,i) ~= 0)
break;
end
end

if(Board(j,i) == 0)
if(j == 6)
row = j;
break;
end
continue;
elseif(Board(j,i) ~= 0)
row = j - 1;
break;
end
end
if(row ~= 0)
numberOfFutureMoves = numberOfFutureMoves + 1;
coordinates(numberOfFutureMoves,1) = row;
coordinates(numberOfFutureMoves,2) = i;
end
end

coordinates(numberOfFutureMoves + 1,1) = 0;
coordinates(numberOfFutureMoves + 1,2) = 0;
end


And I hope this is enough information. Just ask if more information is needed.

I doubt that many people are going to be eager to debug your program for you. Especially given that Matlab is not a common language for game developers. Go back to basics, for example:

- Does it see diagonals as a legal move?
- Does it ever evaluate a configuration with diagonals?
- Force it to evaluate a known board one move away from a diagonal win. What happens?
- Test the values returned for known board configurations. Do they seem right?
- Is it evaluating win/loss conditions correctly?
- Is it performing the min/max correctly, e.g. if it finds a better configuration are variables being updated appropriately?

I don't know if Matlab has proper debugging, but printing output during execution always works.