Coding Games and Programming Challenges to Code Better
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Iâve been lost on this for a bit. Maybe Iâm taking the wrong approach?
Iâm coding in JS, and Iâve had a few different logics Iâve tried out, and it end in one of two ways -
-The code becomes too complex to follow, so I paste my code into a notepad just in case, and start over.
-Limited by the approach
All of my logic seems to start the same. Divide the âformatâ by â~â, and use String manipulation to find the portions of it within âtextâ. This typically works to start, and has been my initial approach.
My first logic worked for every test except the last. I think I know why.
In a situation where the text is ZZABXDABCDFFABYDZZ, and the format ~AB?D?F~
I was working through it, dividing it out by the "?"s after dividing it out by "~"s, and although itâd find an instance of âAB?â in the string, it didnât find the right one, and I hadnât programmed a way for it to backtrack and try the next.
My most recent logic was to separate into two parts. Firstly, the beginning and the end. Thinking if I could separate the special case of if it starts with â~â or not, from the rest of the logic, it might be easier.
Iâm thinking maybe the answer lies somewhere in recursion? When learning programming, recursion is a topic thatâs always given me trouble. I usually am able to understand enough to pass the courses, but never enough to apply it in actual programming. I feel like itâs a valuable tool, but I struggle when applying it.
TL;DR â
I would like help.
Hints, or tips for the puzzle, or learning recursion in a way that I can see how to apply it?
Javascript-specific resources would be nice on the recursion, but Iâm also fine just learning the general logic of it.
Most of the published Python solutions I can see use either regex or recursion, so recursion is definitely a way to go. There are also solutions using dynamic programming and other approaches, but they are very few.
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If youâre not ready for recursion, you can solve this puzzle without it.
- First, write an âequalsâ function, to accept the â?â character (so that âABCDâ and âAB?Dâ would return true).
- Then, write a âfindâ function, using your âequalsâ function (so that it would find âAB?Dâ in âZZABCDZZâ), returning the index.
With those tools, you can just separate words by â~â as you said, and find each word in the text. Be careful about starting each search at the end of the previous one (thatâs why âfindâ returns an index. You start your search at the previous index + previous word.length(), so that âAB~BCâ wouldnât match in âABCâ).
And if itâs too easy with that ⊠you can try recursion. 
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Iâm always sad when I hear this because recursion is supposed to feel a lot more ânaturalâ than programming with loops, so if a teacher makes loops easier than recursion they are doing something wrong in my opinion.
One way to think of recursion is that you have a trusted assistant who already knows how to do the task; you have to make just a little bit of progress yourself, but you can pass most of the task, as a subtask, to your assistant who already knows how to do it.
For instance, imagine you have to match ABXDABCDFF against ~AB?D?F~.
The very first thing to do is decide whether to include the first A into the ~ or not.
If you include it, then youâre left with matching BXDABCDFF against ~AB?D?F~, which you pass to your assistant.
If you donât include it, then youâre left with matching ABXDABCDFF against AB?D?F~, which you pass to your assistant.
So this gives us the following recurrence relation:
match(â~AB?D?F~â, âABXDABCDFFâ) =
Ask your assistant to test match(â~AB?D?F~â, âBXDABCDFFâ) and to test match(âAB?D?F~â, âABXDABCDFFâ), and use the result of these two subtasks to get the result of your task.
Now this is a recurrence relation, you can
- use it directly to write a recursive function
- use it to fill a dynamic programming table where M[i,j] stores the result of match(substring starting at index i, substring starting at index j)
- use it for a stack-based or queue-based approach where you store all the pairs (format,text) that you want to try to match
- or anything else of your choosing.
(Also note I arbitrarily decided to do remove characters from left to right, but you can also do it from right to left if you prefer, ie remove the F before the A)
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ty all for the tips ~
Iâm going to try again later today.
Iâd really like to do it using recursion, so Iâm going to try that first.
Iâll comment again once I triumphantly complete the puzzle >:^)
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Thank you very much for this puzzle, I really enjoyed it.
It reminded me some lessons I had long time ago.
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I DID IT!!! WITH RECURSION!!! (kinda)
I donât know if it still counts as recursion, because I called the recursive function inside of a loop, but it works 
Best part is, would have worked on my first try, but I forgot to pass the previous value of a variable when taking a step back, so it was statically set to false instead of taking a step back and using the previous value.
TL;DR thx for everyone that helped :):):).
Edit:
Iâm now realizing how much simpler this problem would have been to solve with regex xD
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Bonjour, je ne comprends pas pourquoi le test 8 est considéré comme bon.
DĂ©but du texte = IboJSRam>|6&V17T_M|pww)m,<ns8{%9G5%%WT"S=f}kztLQ^eP-T/P-u@?LgbWjnmE
DĂ©but format . = Ibo~ . . . . >|6&~ . . . . . .pw~ )m~ . . . .{~ . . . . . . . . . . . . . . . . . . . -u@?LgbWjnm?/JB<
ça coince ici. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .^
puisque aprĂšs le tiret (-) le format montre un âuâ alors que le texte donne un âTâ
Que nâai-je pas compris dans les consignes ? Merci de mâĂ©clairer.
Hello, I donât understand why test 8 is considered good.
Start of text . .= IboJSRam>|6&V17T_M|pww)m,<ns8{%9G5%WT â S=f}kztLQ^eP-T/P-u@?LgbWjnmE
Start format . = Ibo~ . . . . >|6&~ . . . . . .pw~ )m~ . . . {~ . . . . . . . . . . . . . . . . . . . .-u@?LgbWjnm?/JB<
itâs sticking here. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .^
since after the hyphen (-) the format shows a âuâ whereas the text shows a âTâ.
What did I not understand in the instructions? Thanks for clarifying.
Youâre saying
Text: { %9G5%%WT"S=f}k`ztLQ^eP -T/P -u@?LGbWjnmE/JB<c
~~~~~~~~~~~~~~~~~~~~~~ not matched from here
Format: { ~ -u@?LGbWjnm?/JB<c
But you can also match the format this way:
Text: { %9G5%%WT"S=f}k`ztLQ^eP -T/P -u@?LGbWjnmE/JB<c
~~~~~~~~~~~~~~~~~~~~~~ ~~~~
Format: { ~ -u@?LGbWjnm?/JB<c
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does someone know what is in test Big case, I passed all the tests except the one after submitting the code, I would like to know what is in this test.
Can someone help me please?
In Validator 8 (Big case), the input text is the same as that of Test 8, while the input format is around 50% the same as that of Test 8.
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you fail probably because ~?
Merci pour cet Ă©claircissement.
Certaines consignes mĂ©riteraient dâĂȘtre amĂ©liorĂ©es.
Câest notamment le cas pour le problĂšme âWARâ, la bataille navale, pour lequel jâai vu passer une multitude de demande dâaide concernant le ramassage des cartes.
Ceci dit, jâaurais dĂ» me douter quâil fallait comprendre les consignes diffĂ©remment puisque des participants de "format string validationâ avaient rĂ©solu ce problĂšme. Je rĂ©flĂ©chirai plus longtemps la prochaine fois
Thanks for the clarification.
Some of the instructions could be improved.
This is particularly the case for the âWARâ problem, the naval battle, for which Iâve seen a multitude of requests for help in collecting the cards.
Having said that, I should have known that the instructions needed to be understood differently, as participants in âformat string validationâ had solved this problem. Iâll think longer next time
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I understand what you mean, but it doesnât mean that it will match with the first â-â. Maybe there are more than one character in the text . Thatâs why you have to search till end of the text. As you can see at the second â-â it works.