Just starting this... Problem with matrices

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Just starting this... Problem with matrices

ChipChamp 01 Mar 2008 03:28

Okay, well, I'm trying to recreate a very simple Sudoku game that I made with C++ using TI Basic. I haven't gotten very far because just putting random numbers in my matrix is driving me crazy… So far, this is what I have:

(I'm using TI-83+)

:AxesOff
FnOff
0->Xmin
90->Xmax
0->Ymin
90->Ymax
DelVar A:DelVar B:DelVar C:DelVar D:DelVar Z:Delvar F:0->H
{9,9}->dim([A])
Fill(0,[A])
ClrDraw
For(A,10,100,10)
Horizontal A
End
For(B,10,100,10)
Vertical B
End
Vertical 31
Vertical 61
Horizontal 29
Horizontal 61
Text(1,1,"9
1->C
For(C,1,9)
Lbl 3
1->D
randInt(1,9)->Z
For(D,1,9)
If Z=[A](1,D)
Goto 3
End
Z->[A](1,C)
End
Disp H
Pause
Disp [A]
Pause

Right now, I'm just trying to get 1 random row of numbers 1 - 9, not repeating, in the matrix. The problem is that usually it only ads a few of the random numbers, and the rest are zero. Why doesn't it add random numbers to the entire row?

Thanks for any help, it's been driving me crazy…

Re: Just starting this... Problem with matrices

burr 01 Mar 2008 05:36

Welcome to TI-Basic Developer!

Looking at your code, the problem is with your use of Goto. As a general rule of thumb, you should avoid using Goto unless absolutely necessary because its misuse causes memory leaks and spaghetti code. In this case, the fix is to simply use an If-Then conditional:

:For(C,1,9
:randInt(1,9
:For(D,1,C
:If Ans=[A](1,D:Then
:1→D
:randInt(1,9
:End:End
:Ans→[A](1,C
:End

Last edited on 01 Mar 2008 06:35 by burr Show more

Re: Just starting this... Problem with matrices

Xphoenix 01 Mar 2008 06:26

Strangely, I keep getting ERR:INVALID DIM when running that. The ERR is at the second to last line, when you store to the matrix. [A] is 9 by 9 according to the matrix menu. When I check C and D values, C is 9 and D is 10 (probably because of the last increment). When I change the line

:For(D,1,C

to

:For(D,1,C-1

I get a diagonal of random numbers instead of a row.

On another note, isn't it smaller to create a list of the first 9 positive integers, shuffle it, and then store it to the first row of a matrix?

Re: Just starting this... Problem with matrices

burr 01 Mar 2008 06:35

Ans→[A](C,D is supposed to be :Ans→[A](1,C. I somehow copied it wrong from my calculator. :(

Re: Just starting this... Problem with matrices

burr 01 Mar 2008 06:52

Xphoenix is right that creating a separate list is faster, although it is more complicated. Here is the code for that:

:cumSum(binomcdf(8,0→L1
:rand(9→L2
:SortA(L2,L1
:For(C,1,9
:L1(C→[A](1,C
:End

Re: Just starting this... Problem with matrices

ChipChamp 01 Mar 2008 05:59

Thanks! That did the trick.

And thanks for the tip on Goto. I don't use it in C++ because it's frowned upon, but for some reason I decided to use it in this… Hmm…

Anyway, thanks again! :)

Re: Just starting this... Problem with matrices

burr 01 Mar 2008 06:06

I'm glad I could be of assistance. How long have you been doing C++?

Re: Just starting this... Problem with matrices

ChipChamp 01 Mar 2008 06:13

I started learning it on my own about 2 - 3 years ago… But it's been kind of off and on, so I've probably only been programming in it for about 1 year.

I prefer to use Java nowadays, though I've only been doing that for a few months. :)

Re: Just starting this... Problem with matrices

burr 01 Mar 2008 06:18

Java is a fun language, although there's a lot to learn.

Re: Just starting this... Problem with matrices

ChipChamp 01 Mar 2008 06:24

True, although it seems much more simple than C++.

Re: Just starting this... Problem with matrices

burr 01 Mar 2008 06:53

If you get comfortable enough with it, you can consider getting certified.