DWITE October 27th - My solutions

[MysticVegeta]

Here are my solutions, please use them as a source, dont copy and paste and say they are yours!!

Please tell me how i could kiss the code. thanks a lot!

[Cervantes]

I've only looked at number 4 so far, but one thing that stood out to me was your huge if structures for checking around. Instead, try using two for loops, from -1 to 1 (or from 1 less than the grid coord to 1 greater than it). Keep in mind you'll have to have an if statement to prevent checking when both for loops are at zero.

[MysticVegeta]

yeah, I didnt kiss my code, i was in a rush so i did everything i could from the top of my head, i need practise to be more code lines saver, By the ways, i cant see my attachment anymore, waht happened?

[zylum]

here's a solution to #5:

code:

var file : int open : file, "DATA51.txt", get var ret, d1, d2 : int var s := "123456789" proc perms (n, cp : string)     if length (n) = 0 then         if strint (cp) mod d2 = 0 then             ret += 1         end if     else         for i : 1 .. length (n)             perms (n (1 .. i - 1) + n (i + 1 .. *), cp + n (i))         end for     end if end perms for i : 1 .. 5     ret := 0     get : file, d1, d2     perms (s (1 .. d1), "")     put ret end for

[Hikaru79]

What exactly do you mean by "kiss my code"? You've used it three times so far, and I still giggle whenever I read it. Does it mean something besides what I think it means?

[MysticVegeta]

KISS - Keep it Simple Student, never heard of it? every teacher says that lol

Anyways, zylum. I cant use that, thats what i did before but it wont give me a perfect, i read your permutations tuts before too. The data file has 5 lines of Data. what if n1 is 9, it takes forever to check for it
it wont execute on time. i know theres some way around it. Even Qiyu spent more than 40 minutes on this problem, rest he took like 10-15 minutes. There is some other way, i think

[Cervantes]

I was wondering about that too, but I think I've figured it out.
KISS = Keep it Simple, Stupid.

Hard to get because no one would say,

Quote:

yeah, I didnt keep it simple, stupid my code

MysticVegeta wrote:

By the ways, i cant see my attachment anymore, waht happened?

I see your attachment.

[MysticVegeta]

yeah, now i see it, problem 5 is weird, i think we have to make up the prime factors for the divisor given and then perhaps try it but still confusing.

[zylum]

meh, there's only ~360000 permutations of a 9 digit number. thats penuts. its probably that turing is so slow. im sure if you submitted it in c++ it would have been more than fast enough.

i guess ill try to code a faster solution then...

[jamonathin]

Cervantes wrote:

I was wondering about that too, but I think I've figured it out.
KISS = Keep it Simple, Stupid.

It is 'Stupid' not 'Student'. Doesn't anyone remember my old signature? . .

[MysticVegeta]

jamonathin : our teacher didnt say stupid, because that wouldnt make sense coming from a teacher now would it?

zylum : even C++ will time out. Because there are 5 sets of data. maybe VC++ will compile...?

[JackTruong]

Problem5 was a tricky one, our initial code (the one we submitted) was actually find the permutation with unique digits, and modulus it to output.

I just worked out another solution, this one's faster, but it won't execute the input of "9 2" in a few seconts.

We had this idea during the competition, but coding it in 14 minutes was a huge task.

Pseudo:
Start with string from 1 to 9, substring it.
Find a multiple of the second number, at or above the string above.
Run a for loop, from the number above, to the reverse of the above string, and incrementing the second number each time.
Run a check for proper digits.
Run a check for unique digits.
Increment a counter.
Output counter.

I typed this post and the "9 2" input is still going. Source code will soon be uploaded to a section of my site dedicated to DWITE; Link..

Other problems are up too, with some partial explanations.

[MysticVegeta]

wont that time out by substringing the 9 digit string? and reversing it everytime.?

[JackTruong]

No, it's just a one time event.

Source

[MysticVegeta]

I see Jack.
My approach to it is something like this ->

5 12

12345 all divisible by 3 because 1+2+3+4+5 = 15
XXX12 -> XXX satisfies 6 values in each case
XXX24
XXX32
XXX52
So Number of possible values are 6X4= 24

This was the example from the problem.

So my strategy is like this

1) Since we know the divisibility for 2,3,4,5,6,7,8,9,10,11 then we can break up the divisor from 2 - 50 into factors {2..11} where no two factors are alike.

2) Then find the number of possible values by each of the factor ->
Ex: suppose 123456789 is the string and d1 = 10
then,

22 = 5 * 2

XXXXXXX2
XXXXXXX4
XXXXXXX6
XXXXXXX8

Possible values for 2 : (!8)*4 = 40320

XXXXXXX5

8! = 10080

but 5 is not even so intersection of mutiples is 0; so possible number of values is 0, should work with other numbers

EDIT: For prime numbers, http://home.egge.net/~savory/maths1.htm