730 - Morse Code Generation

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Ivor
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730 - Morse Code Generation

Post by Ivor » Wed Jan 23, 2002 11:44 am

I'd be glad if someone could explain me the sample io, for as much as I have figured out, it seems wrong.

I can't understand, where to get the 115ms dotlength for 13 wpm transmission. If to divide 60 sec by 624 dot spaces, the answer is 96 ms. I could get 115 ms when I counted only 13 words and not the spaces between words, so 1 min / 65 / 8 = 115 ms.

And the value of 1428 ms for 55 wpm transmission is the one, especially mysterious.

Thanks,
Ivor

..
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Post by .. » Wed Jan 23, 2002 4:34 pm

Hi,
I am one of the people solving this question, but I am sorry to tell you that: I still don't understand what the question means..........

I can tell you that:
1. You assumption is correct, you should calculate the dot space w/o space between chars (but I don't know why......)

2. formula for char space when speed < 13:
(60000.0-(dot_length*5*speed))/(speed*8)

3. the above fact is extarcted from
http://www.acm.inf.ethz.ch/ProblemSetAr ... 91/morse.c

I have spent a lot of time to think about the relationship between these formulas and the problem description. But I have no discovery.........
If anyone discovers the realtionship between the formulas and the problem, PLEASE tell me~~

My conclusion on this question is:
the problem description is very very mis-leading.......
Last edited by .. on Thu Jan 30, 2003 7:35 am, edited 1 time in total.

Ivor
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Post by Ivor » Wed Jan 23, 2002 9:48 pm

I took a look at the code and found some curious things.

1: in function init
dot_length = 60000 / (8 * (5+1) * 13 );
/* established default dot length for 13 wpm */

It counts 5 characters per word + 1 space character between words.

2: in function figure_speed
dots_per_min = (long int) 8 * 5 * 13;
dot_length = 60000/dots_per_min;

Now there is only 5 characters per word and NO spaces between words!

So I can't really understand the thing. Points 1 and 2 speak against eachother, it seems as if the author didn't quite get what he had to compute. As a proof of this I'd like to point out the three question marks at the end of the figure_speed function.

If that is the case then all the test data should be revised. If not, please correct me.

Thanks,
Ivor

Caesum
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Post by Caesum » Wed Jan 29, 2003 7:55 pm

I think this question was revised ? Anyway, it seems straightforward as it is all based on 60000/(40*wpm)

..
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Post by .. » Thu Jan 30, 2003 7:35 am

Yes, thanks to the effort of judge, this problem is rejudged. And the logic of this problem become more reasonable now~~
My signature:
  • Please make discussion about the algorithm BRFORE posting source code.
    We can learn much more in discussion than reading source code.
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  • Don't send me source code for debug.

edfigo
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Post by edfigo » Thu Jul 03, 2003 8:29 pm

I just don't understand the formula for char space (when wpm < 13)...
The intra-character is allways: 6000/(wpm*5*8)
and the char space (inter-character) is 3 times intra-character!
The dot length is:
=6000/(13*5*8), for wpm<13 or
=intra-character, for wpm>=13

Another thing, i think that could be exists some characters with diferent morse code representation than the ones show in the table, 'cause in my first attempt i just "copy n paste" the table but gives me WA!

I hope this helps!
edfigo

edfigo
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Post by edfigo » Thu Jul 03, 2003 8:36 pm

...some corrections for previuos post...
when i wrote 6000, i mean 60000 and the 8) is an 8 and )
edfigo

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