Matrix and element change and input help

2013 5 23
2 个回答
回答已采纳
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0 个投票

This may be trivial but how do I get for a user input coords as a matrix, and to change the element to another number eg. a tic-tac-toe game player 1 inputs a coord to change a 0 in the matrix to a 1, and player 2 changes a 0 to -1. (player==0 when it is player 1's turn)
my code:
I=input('Number coordinate: ');
for a=1:3
for b=1:3
if B(a,b)==0
if I==1
if player==0
B(1,1)=1;
else
B(1,1)=-1;
end
elseif I==2
if player==0
B(1,2)=1;
else
B(1,2)=-1;
end
elseif I==3
if player==0
B(1,3)=1;
else
B(1,3)=-1;
end
elseif I==4
if player==0
B(2,1)=1;
else
B(2,1)=-1;
end
elseif I==5
if player==0
B(2,2)=1;
else
B(2,2)=-1;
end
elseif I==6
if player==0
B(2,3)=1;
else
B(2,3)=-1;
end
elseif I==7
if player==0
B(3,1)=1;
else
B(3,1)=-1;
end
elseif I==8
if player==0
B(3,2)=1;
else
B(3,2)=-1;
end
elseif I==9
if player==0
B(3,3)=1;
else
B(3,3)=-1;
end
end
else
disp('That is an invalid move')
end
end
end
problems with it: It will let a user set a piece on an already used part of a matrix and will always say that it is an invalid move (even if it is valid)
Could anyone help me to find a good way to do this?
-thanks, Alex

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 采纳的回答

David Sanchez
David Sanchez 2013-5-23

0 个投票

I think you are trying to do just this:
BB = reshape(B',9,1);
I=input('number coord:');
player = 1;
BB(I) = 2*(player == 0) - 1;
B = reshape(BB,3,3)';
aren't you?

7 个评论
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David Sanchez
David Sanchez 2013-5-23
with
player = 0;
you'll get -1 instead of 1
Alex
Alex 2013-5-23
This works, but I'm not sure I can understand it, could you explain it to me?
Sorry if I explained my problem as well.
David Sanchez
David Sanchez 2013-5-23
I guess you are having problem in understanding this sentence:
BB(I) = 2*(player == 0) - 1;
Matlab accepts logic assignment such as above. (player == 0) will be either 1 or 0, since its a logic assignment ( watch the double = ). When player = 0, (player == 0) yields 1, and then:
BB(I) = 2*0 - 1 = -1
When player = 1, (player == 0) yields 0, and then:
BB(I) = 2*1 - 1 = 1
Alex
Alex 2013-5-23
Thankyou very much :)
Alex
Alex 2013-5-23
One more thing, how would you show if the input is valid or not (as an input must be a coordinate to an element with only a 0 in it).
David Sanchez
David Sanchez 2013-5-23
Do you mean this?
I=input('number coord:');
if ismember(I,1:9) % this checks whether I equals 1 2 3 4 5 6 7 8 or 9
BB = reshape(B',9,1);
player = 1;
BB(I) = 2*(player == 0) - 1;
B = reshape(BB,3,3)';
end
Alex
Alex 2013-5-23
I mean if the matrix has a -1 or a 1 in it already (this code will be in a loop), how can I find if it is in an already used spot, display that the input is invalid, and replay the input to give the user a chance to input a proper coordinate

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