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thornahawk
μολών λαβέ
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 Posted: 07 May 2007 04:43:06 am Post subject: |
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Meanwhile... I have here a nice and easy  brain teaser for everybody:
You have two matrices of (possibly) different dimensions stored in [A] and [B]. Write a program (as short and/or as efficient as possible) that stores the Kronecker product [A]⊗[B] into matrix [C].
:D
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Harrierfalcon
The Raptor of Calcs
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| Posted: 09 May 2007 06:22:25 am Post subject: |
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Possibly. Could you clarify what the elements of the matrix should hold?
EDIT: Never mind, a quick glance at Wikipedia clarified. Now, about these elements...
Last edited by Guest on 09 May 2007 06:26:33 am; edited 1 time in total |
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thornahawk
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| Posted: 09 May 2007 06:31:14 am Post subject: |
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I'll give an example to clarify for everybody:
If
[A]=[[1,2][3,4]] and [B]=[[1,1,1][1,1,1]]
then [C] should contain
[[1 1 1 2 2 2]
[1 1 1 2 2 2]
[3 3 3 4 4 4]
[3 3 3 4 4 4]]
;)
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Harrierfalcon
The Raptor of Calcs
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| Posted: 09 May 2007 06:32:08 am Post subject: |
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Making to work for any dimensions is the biggest problem, methinks.
Last edited by Guest on 09 May 2007 06:32:15 am; edited 1 time in total |
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thornahawk
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| Posted: 09 May 2007 06:35:04 am Post subject: |
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It's not that hard. I'll post my solution after I see at least two attempts.
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Harrierfalcon
The Raptor of Calcs
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| Posted: 09 May 2007 06:45:45 am Post subject: |
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| How many bytes is it? I just want an idea of if i should be using built-in functions or For( loops... |
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thornahawk
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| Posted: 09 May 2007 07:08:50 am Post subject: |
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Not counting the program name, the solution I have is 85 bytes. I'm ready to see smaller programs, if there are. ;)
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DarkerLine
ceci n'est pas une |
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| Posted: 09 May 2007 05:28:58 pm Post subject: |
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thornahawk wrote: Not counting the program name, the solution I have is 85 bytes. I'm ready to see smaller programs, if there are. ;)
thornahawk
[post="103450"]<{POST_SNAPBACK}>[/post] Right now I have two solutions, both 87 bytes without the program name. I'm working on finding out what I'm missing. |
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Harrierfalcon
The Raptor of Calcs
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| Posted: 09 May 2007 07:45:02 pm Post subject: |
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If you insist...
Code:
:dim([A])dim([B->dim([C]
Yeah. That's as far as I got. |
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thornahawk
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| Posted: 13 May 2007 04:47:46 am Post subject: |
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The solution to the Kronecker product teaser:
(highlight below)
dim([A]→L1
For(I,1,L1(1
[A](I,1)[B]
For(J,2,L1(2
augment(Ans,[A](I,J)[B]
End
If I>1
augment([C]T,AnsT)T
Ans→[C]
End
[C]
:)
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DarkerLine
ceci n'est pas une |
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| Posted: 13 May 2007 11:26:20 am Post subject: |
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I had much the same thing, but couldn't think of the right way to handle the [font="courier new;font-size:9pt;line-height:100%;color:darkblue"]If I>1 case (I had an If-Then-Else loop).
I partially compensated for that with an optimization that works on the calculator even though it makes no mathematical sense: you can replace [font="courier new;font-size:9pt;line-height:100%;color:darkblue"][A](I,1)[.B] with [font="courier new;font-size:9pt;line-height:100%;color:darkblue"][.B][A](I,1 to save a byte, and the same for [font="courier new;font-size:9pt;line-height:100%;color:darkblue"][A](I,J. Using [font="courier new;font-size:9pt;line-height:100%;color:darkblue"]Ans(1 in the first For( loop, and using [font="courier new;font-size:9pt;line-height:100%;color:darkblue"]LA instead of [font="courier new;font-size:9pt;line-height:100%;color:darkblue"]L1 helps too.
Oh and here's a 65-byte (ignoring the title) program for a matrix with a border:
[font="courier new;font-size:9pt;line-height:100%;color:darkblue"]List>matr(binomcdf(9,0),augment({1},binomcdf(8,1)),[A]
augment({1},binomcdf(16,1
List>matr(Ans,not(Ans),[.B]
[A][B]T->[A]
I suppose it also has the useful trait of being independent of matrix size (you can just change the numbers and it will work).
Last edited by Guest on 13 May 2007 01:45:00 pm; edited 1 time in total |
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TI-Basic Brain Teasers => TI-BASIC
